Is there any working Quake World client? I've tried powerup version from Aminet but it freeze my system...

Yeah I'm just looking at that problem now. You can use the WOS version (qwclWOS), that runs fine with -nocdaudio and -nosound, but of course you don't get any sound
Does anyone know if you can get AHI working on it- there's nothing in the docs?

And you probably already know, to make the stack 500,000 too.

If you had a Voodoo3, you might be able to use BlitzQuake, but that's a GL-only exe- I haven't tried it myself though.

Frank Wille did do a MorphOS version of the QuakeWorld client, but I don't think he ever released it.

Maybe you could send him a friendly email and ask him?

The Sourcecode of the Amigaversion is avalable.
Should be relatively easy to adapt it to MorphOS.