No fight between us : that's our ennemis want...
Your enemies? There's no need to try to make me look like an antagonist for pointing out these issues.
To be clear : I have only added some asm 060 Mul64 parts into the source, nothing more since I'm a super beginner in C, I cannot do more, sorry...
You were able to simply add those to the source because the source code of the port was made available to you by Dante. Dante was able to port it to the Amiga because the original source was made available to him by 3D Realms & Ken Silverman. The point of GPL is that if you'd actually comply with it, someone else could just as easily improve on your efforts.
If anyone else in this chain had the same attitude to the license as you do, you wouldn't have been able to modify and improve on the source code.
Who gives a f**k if someone releases a FREE patch to a very old PC game without providing the patch source code, who is actually getting hurt by this action?
If I walk into your house and just stand there without doing anything, who is actually getting hurt by it? Probably no one (maybe me, if you found out), but since I respect your property and I respect the law (besides having no personal interest in doing so) I won't do that anyway.
You can also look at it like this: Who would have been "hurt" if Dante hadn't released his source? Certainly, changing a few lines of code in his source to produce a faster Amiga port wouldn't have been possible. Who would have been hurt if 3D Realms didn't release the source in 2003? An Amiga port would have been a massive undertaking.
What GPL does is set up a definition of "FREE" that is more permissive than exclusive copyright but with the caveat that derivative works also need to be "free" under the same conditions. Apart from that it permits you to do basically anything. If you don't agree with that definition of "free", you don't have to use or derive your software from GPL software. It's simple to opt out, but it's also very simple to comply by including the license information and dumping the source you built your binaries from somewhere that people can reach it. I equally don't understand what the fuss is about.
Some people obviously prefer to complain than to step up and do something productive themselves.
Say whatever makes you feel better.