As someone who's worked in AAA game engines this is like saying because C# is now open source it will be easy to just copy code into Swift without any hassle.
The part that makes game engines both interesting and difficult is they made a series of discrete trade-offs to support the use cases of the types of games they ship. This is true from tooling workflows to rendering stacks to core engine layout like if they do heavy arena allocation or more open world dynamic entities.
We extended the engine we licensed with some fairly reasonable features and even doing the uplevel was a brutal, 4-6 month process to reconsile those changes.
The part that makes game engines both interesting and difficult is they made a series of discrete trade-offs to support the use cases of the types of games they ship. This is true from tooling workflows to rendering stacks to core engine layout like if they do heavy arena allocation or more open world dynamic entities.
We extended the engine we licensed with some fairly reasonable features and even doing the uplevel was a brutal, 4-6 month process to reconsile those changes.