Copyright violation. If you write a book and I translate it to a different language you own the copyright on my translation. (except poetry which is artistic enough that it cannot be translated and so your version inspires me but I can't just translate it ). Decompilation doesn't have enough creative work to call it anything other than a translation.

I'm not a lawyer. I'm reasonably sure I'm right so the above is good enough for discussion, but if you need legal advice see a lawyer.

This project compiles to identical binary to the original one. Distributing this source is the same as distributing the game in practice.