Just a quick status update: I'm done with the MorphOS port of ET:L, it now runs stable on my machine. I've also compiled all the mods I have the source of: etmain, etpub, nq 1.2.7. The authors of silent mod will compile a morphos version for me, but there are still some unresolved issues there.
The next stable version 2.71rc3 has been tagged a couple hours ago, so if everything goes well you can expect a morphos version very soon (I have to add my pure-server hack, and compile+package everything - the usual jazz). The game is a bit more demanding than RTCW, with all the open areas and players, but it should be playable on faster G4 machines.