Sell game source code: what the engine lets you keep and pass on

The code your team wrote, yes, if the studio holds its copyright. Unreal's EULA says you own all rights in the products you develop, other than rights in the engine itself. What you cannot sell is the engine, store-bought assets or middleware inside the project, which their own licences keep. (Game middleware software data terms: every row, with its source)

Not with the assets as they stand. The Asset Store EULA lets a buyer distribute an asset only as incorporated and embedded in a licensed product, and its clause (g) bars using assets to train an AI or machine learning model without the express consent of the provider or Unity. (Game middleware software data terms: every row, with its source)

Your own code, yes; the engine code, no. Unreal lets you distribute engine code only to a third party separately licensed by Epic for the same version, and its EULA bars any use that results in the licensed technology becoming a training input to a generative AI program. (Game middleware software data terms: every row, with its source)

Their code stays with them. FMOD's EULA allows only the FMOD Engine run-time libraries to be distributed, Havok says redistribution outside the licence agreement is prohibited, and the Spine Runtimes require each user of a product to hold their own Spine Editor licence. (Game middleware software data terms: every row, with its source)

Yes, in both the US and the UK. US law defines a computer program as a set of statements or instructions used in a computer to bring about a result, and the Copyright Office treats source code and object code as two representations of the same work. (Game middleware software data terms: every row, with its source)

On this board, 0 of the 19 licences reserve an aggregated or anonymised copy of a studio's data, and none of them says the vendor may train its own models on it. (Game middleware software data terms: every row, with its source)