Game Engine Licensing After Unity's Runtime Fee: What Your Studio's Legal Exposure Actually Is

What Unity's Runtime Fee Controversy Was — and the Legal Questions It Raised

To understand the legal exposure, you need the three-act sequence. The story doesn't start in September 2023 — it starts in 2019, when Unity used a Terms of Service modification to prohibit developers from using Improbable's SpatialOS platform. The developer backlash was severe enough that Unity responded with a protective commitment: if Unity updated its terms in a way that adversely impacted developers, they could elect to continue under the terms that applied just prior to the update. That clause lived in Unity's TOS for four years.

On April 3, 2023 — five months before anyone heard the phrase "runtime fee" — Unity quietly removed that protective clause. No announcement. No prominent disclosure. The clause that had been specifically designed to prevent retroactive TOS harm to developers was gone before the fee that would require it was ever announced.

Then, in September 2023, Unity announced its runtime fee: a per-install charge that would apply to games already in distribution — meaning studios would owe fees on titles they had shipped under entirely different licensing terms. The removal of the protective clause five months earlier was not incidental. Without it, developers had no contractual hook to argue they were entitled to stay on prior terms.

The operative legal theory developers would have pursued is unconscionability under California law — Unity's governing law since October 2022. California courts require a contract provision to be both procedurally and substantively unconscionable to be unenforceable. Unity's TOS is a contract of adhesion — a standardized agreement imposed by a party with vastly superior bargaining power — which satisfies the procedural prong. Retroactive fees imposed on licenses that were already fully executed could have met the substantive threshold, though that analysis was never tested in court.

That last point matters enormously. In September 2024, Unity abandoned the runtime fee entirely, reverting to seat-based subscriptions — Unity Personal free under $200K/year in revenue, Unity Pro at $2,200/year above that, Unity Enterprise required above $25M in total annual revenue or funding. The pricing changes took effect January 1, 2025. Unity backed down because the market walked toward Godot and Unreal, not because a court ordered it to. The unconscionability question — whether a game engine licensor can retroactively impose fees on games already in distribution after quietly stripping the clause that would have prevented it — remains entirely unresolved as a matter of law. The next studio to face a similar move from any engine licensor will have no precedent to rely on.

Unreal Engine's Royalty Structure: The $1 Million Threshold and What It Measures

When studios evaluate Unreal Engine as a Unity alternative, they usually walk away with one number: 5%. That's the royalty rate. What they often miss is the denominator — and the denominator is where the legal exposure lives.

Unreal's standard EULA requires a 5% royalty on worldwide gross revenue once a product has earned $1 million in lifetime gross revenue. Lifetime, not annual. The $1 million threshold does not reset at the start of each calendar year — it measures cumulative earnings across the product's entire commercial life. A studio that earned $900,000 in year one and $200,000 in year two owes royalties on the $100,000 that crossed the threshold in year two, even if the game's revenue has declined. That single distinction changes the financial model for any game with a long tail.

What "Gross Revenue" Sweeps In

The EULA defines gross revenue to include all revenue directly generated by the product, regardless of how it's collected. That means base game sales, DLC, in-app purchases, microtransactions, subscriptions, and virtual currency redemption all flow into the same royalty pool. For a live-service studio, this isn't a footnote — it means that a game earning $800,000 in base sales and $300,000 in season pass revenue has already crossed the threshold before the third season launches.

Three accounting questions follow from this definition. First: what revenue pool am I measuring? All product-generated streams, consolidated. Second: when does the meter start? At first commercial sale, counting forward indefinitely. Third: does the $10,000 quarterly floor help? Somewhat — Epic does not require royalty reporting for any quarter in which gross revenue falls below $10,000, and payments for those quarters are excluded. But the revenue still counts toward the lifetime total; it just doesn't trigger a quarterly filing obligation.

The Epic Games Store Exclusion and the Bifurcated Ledger

One structural feature of the EULA creates a meaningful accounting split. Revenue from sales processed through the Epic Games Store does not count toward the $1 million lifetime threshold. A studio that routes a portion of its sales through EGS effectively runs two parallel revenue ledgers — EGS revenue stays off the royalty clock entirely, while revenue from Steam, direct sales, or other storefronts accumulates toward the threshold. For studios with significant EGS distribution, this bifurcation isn't optional bookkeeping; it's a contractual compliance requirement.

The 3.5% Rate and What It Requires

Since January 1, 2025, Epic's Launch Everywhere with Epic program offers a reduced royalty rate of 3.5% — down from 5% — for games that launch on the Epic Games Store simultaneously with or before other online stores. The program applies to Windows, macOS, and Android releases. The catch is a marketing obligation: the Epic Games Store must receive "equivalent" promotional prominence to other stores in all marketing materials. This isn't a passive licensing discount; it's a distribution commitment with merchandising strings attached.

For studios negotiating their engine contracts, the gap between 3.5% and 5% on the $4 million subject to royalties (revenue above the $1M threshold) is $60,000. That's a material number, and it's the kind of software licensing analysis that belongs in a studio's financial model before a distribution strategy is set — not after. The royalty structure doesn't just describe what you owe; it shapes which platform you launch on first.

Godot's MIT License: What "No Royalties" Covers (and What It Doesn't)

Godot is released under the MIT (Expat) license — not Apache 2.0, a distinction that carries real legal weight. The MIT license grants unrestricted commercial use, modification, redistribution, and sublicensing with no royalties, no runtime fees, and no per-seat charges. You can ship a commercial game built on Godot, charge whatever you want for it, and owe the Godot Foundation nothing.

Attribution in your game binaries is also not required. You do not need a "Powered by Godot" splash screen or credit block — the license imposes no such obligation on the compiled game itself. What you do need is to make the MIT license text accessible to your end users — covered in the section below.

What the License Text Requires

The MIT grant has one mandatory compliance obligation and one strongly recommended best practice. The requirement: include the MIT license text somewhere accessible in your distribution — a credits screen, a licenses menu, an accompanying text file, or a link all satisfy this. The best practice: address the bundled third-party components that ship inside the engine by including GODOT_COPYRIGHT.txt alongside your game — Godot's documentation recommends this. These third-party components carry their own licenses — MIT, BSD, and similar permissive terms — and while omitting the file isn't a violation, it's a gap worth closing.

Critically, none of this forces your game code open. Godot's MIT license is not copyleft. Your proprietary game logic, assets, and scripts stay proprietary. You can license your game however you want — commercially, via a custom EULA, or under any other terms you choose.

What the AS IS Disclaimer Takes Away

The license's warranty disclaimer strips out protections that commercial engine agreements sometimes provide. Godot comes with no warranty of merchantability, fitness for a particular purpose, or non-infringement. The Foundation makes no representation that the engine is bug-free, will continue to be maintained, or will not conflict with third-party IP. There is no support SLA and no contractual recourse if an engine defect ships in your product.

For most studios, this is an acceptable trade-off — the engine is free, the community is large, and the risk of a catastrophic undisclosed engine defect is low. But it is a different risk posture than a commercial license with indemnification provisions.

The Patent Gap

Here is the nuance that matters most in patent-sensitive commercial environments: MIT does not include an express patent license. Apache 2.0 has a dedicated patent grant in Section 3 — contributors explicitly license any patent claims covering their contributions. MIT has no equivalent clause.

In practice, this means a Godot contributor who holds a patent on a technique implemented in the engine retains the ability to assert that patent against you, even though you are using the engine in full compliance with its license. The MIT license extinguishes copyright claims only. For most indie studios, this risk is theoretical. For studios operating in areas with dense patent activity — physics simulation, procedural generation, audio compression — it is worth flagging to counsel before you commit your entire codebase to a single engine architecture.

Evaluating Your Studio's Engine Dependency Risk

Unity retreated from its runtime fee under commercial pressure, not a court order. No judge ruled on whether those changes were enforceable. The legal question — whether a game engine TOS can retroactively impose new fees on games already in distribution — remains open. That ambiguity is itself a risk factor your studio should price in before committing to any engine for a multi-year project.

The framework below gives you four questions to answer for any engine you evaluate. The answers tell you how much legal exposure you're accepting — and how much leverage you'd have if the vendor tried to do what Unity attempted.

Question 1: Unilateral Modification Clauses

Unity added California choice-of-law language to its TOS in October 2022. Under California doctrine, an agreement can only be voided for unconscionability if it is both procedurally and substantively unconscionable. A standardized TOS imposed by a party with vastly superior bargaining power likely clears the procedural bar. Whether any specific fee imposition crosses the substantive threshold is a fact-specific question a court hasn't answered.

A 2024 decision from the Eastern District of Virginia, Lovinfosse v. Lowe's Home Centers, held that a TOS clause authorizing modification "at any time and without notice" rendered the entire agreement illusory and unenforceable. That case arose in a retail arbitration context — not software licensing — and Virginia law governed, not California. The reasoning doesn't translate directly. But it illustrates a developing judicial skepticism toward open-ended unilateral modification clauses, and it's the kind of argument developers would raise if a fee dispute ever reached litigation.

Questions 2 and 3: Acquisition and Shutdown Risk

Unity and Epic are both corporations whose TOS can be amended by whoever controls them. An acquirer inherits the IP, the developer relationships, and the right to modify terms on whatever notice the agreement allows. Godot's structure eliminates this vector: copyright over Godot's source code is held collectively by every contributor, the Godot Foundation is a legally independent non-profit registered in the Netherlands, and it does not own the engine. There is no single entity whose acquisition could transfer control over the codebase to a buyer.

The contributor model also addresses shutdown risk. Godot contributors do not sign a Contributor License Agreement, which means they individually retain copyright in their contributions. If the Foundation dissolved, no one's right to maintain or fork the engine would be extinguished — the project would continue under whichever contributors chose to keep it alive. With a proprietary engine, a shutdown leaves you dependent on whatever source-code access your license grants, which for most commercial tiers is none.

The Switching Cost Factor

Engine migration mid-project is expensive in ways that don't appear on any TOS page. Rendering systems, physics integrations, asset pipelines, and platform export configurations are engine-specific. A studio three years into an Unreal project that decides to move to Godot faces schedule risk that can dwarf any licensing cost. That switching friction is itself a form of lock-in — and it's one reason the legal terms of your initial engine choice matter more than they might appear when you're starting pre-production.

Running this four-question analysis before committing to an engine doesn't guarantee you'll avoid every legal exposure. But it surfaces the specific risks Unity's 2023 crisis made real — retroactive fees, acquisition scenarios, and shutdown contingencies — before your studio's technical debt makes switching prohibitive.

Publisher Contracts and Engine Terms: What Indie Studios Should Negotiate

Signing a publishing deal after Unity's 2023 fee announcement meant studios faced a compounding problem: publisher agreements typically require developers to warrant — not merely represent — that the game complies with all third-party license terms. A representation is a statement of fact at signing; a warranty is a promise that it stays true for the duration of the deal. If your engine company changes its terms after you sign, that warranty can put you in breach through no fault of your own.

The fix is a knowledge qualifier. Push to limit any engine-compliance warranty to "to the best of Developer's knowledge" language. That phrasing restricts your liability to issues within your reasonable awareness — it excludes unilateral TOS changes the studio had no way to anticipate. Without it, you're underwriting risk that sits entirely outside your control.

The Open-Source Problem for Godot Studios

Some publishing agreements contain a flat prohibition on open-source software: the developer warrants that "no Open Source Software is or will be incorporated into the Game." For studios building on Godot — which ships under the MIT license — this clause is an automatic breach. Before signing, locate and remove it, or negotiate a specific carve-out for MIT-licensed engine code.

This isn't a theoretical edge case. Publishers typically draft these clauses with copyleft licenses like the GPL in mind — licenses that can impose downstream obligations on commercial products. MIT carries no such burden, so the business concern that drove the clause doesn't apply to Godot. Most publishers will accept a narrowly drafted carve-out once the distinction is explained.

Financial Architecture: Unreal Royalties as a Deduction

If your studio is shipping on Unreal Engine and expects to cross the $1 million lifetime gross revenue threshold, the 5% royalty becomes a line item that publishers will recoup against — unless you structure the deal otherwise. The correct position is to treat the Unreal royalty as a deductible expense carved out of the revenue base before the publisher's profit split is calculated. Without that deduction, you may spend substantially longer in recoupment, because the publisher is recovering its advance against a gross figure that already includes the royalty drag you're carrying.

Source Code Escrow

For studios licensing engine technology — particularly proprietary middleware or custom engine variants — source code escrow is a legitimate protection worth requesting. The structure is straightforward: the studio deposits engine source code and build dependencies with a neutral escrow agent, who releases the materials only if defined trigger events occur, such as engine vendor insolvency, cessation of support, or a material breach of the license agreement. Smaller studios are unlikely to win this provision from a major publisher, but it costs nothing to request it and belongs in the negotiation record.

Your engine choice is also a contract decision. The representations you make at signing, the open-source clauses buried in boilerplate, and the revenue waterfall structure all carry legal weight that outlasts the launch window. Studios that identify these pressure points before the deal closes have far more leverage than those who surface them during a dispute.