Parts of source code in project

Hello,
Is it legal to use (copy and modify) methods and parts of methods from source code in unreal engine project?

Best regards.

The Unreal Engine EULA allows you to use the source code directly.

I don’t know how directly use of source code works, so can I copy and modify part of engine source code and paste it in unreal engine project?

Best regards

Under the EULA, you can use as much or as little of the Licensed Technology as you like, including parts of the engine code. The resulting product will be a Product as defined in the EULA.