"I didn't want to imply that the author is in violation. But the licence of MiniGL prohibits the usage of the library on non-AmigaOS systems. This includes all MiniGL games (including Heretic II and Quake II)."
I had a read of your link, and it says:
"MiniGL may only be compiled for/ incorporated in code running on AmigaOS. All other rights reserved. This applies only to MiniGL, not to your application, i.e. It's OK to port the application to another platform using OpenGL."
So where on earth does it say that end users can only use this library on Amiga systems - nevermind that such a restriction has no legal weight, it doesn't even say it in the licence.
What the licence says as far as I can tell is that someone can not use it to compile something for a platform other than AmigaOS (and then distribute it). This is legally enforceable, because to distribute a program based on this library, you're distributing some of the code, and so must abide by any terms.
But if the program is compiled for AmigaOS, but someone emulates that on another OS, that's touch luck (unless Hyperion are able to succeed in court better than Sony and Microsoft?)
Now, let's RTFA:
http://www.nic.fi/~varsa/d3gnop/index.html"Requirements
"Amiga with at least 68040 (PPC is supported via WarpOS) or compatible"
Suggests it's been compiled for AmigaOS. And to be sure, "The game should also run on other compatible platforms/under emulation with right setup (MorphOS, WinUAE)." Note, *emulation*.