I think could have been a hot topic at the dawn of game development. Nowadays it’s irrelevant. Starting with Wolf3D and up to Doom 3, idSoftware released entire engine and gamecode, for free. To the date no one (maybe one team did) took advantage and either used the code as-is or built on top of that, for a commercial game dev. Worth mentioning that it’s a solid example of how to write decent gamecode framework. Even with that people didn’t use it.
What makes anyone think that someone will go to extreme of decompiling your game code? o.O
Devs with money would license your code, and devs without money wouldn’t be able to do much with decompiled code anyway.