Couple of things.
1. Quake III's system requirements are rediculously low by today's standards.
3D graphics accelerator with full OpenGL support, Pentium II 233 MHz or AMD 350 MHz K6-2 processor or Athlon processor, 64 MB RAM, 8 MB video card, 500 MB of free hard drive space, 100% DirectX 3.0 or higher compatible sound card, CD-ROM drive (600 kB/s sustained transfer rate)
Even though it's not an x86, the Cortex-A8 in the N900 combined with its OpenGL 2.0 compliant PowerVR gpu has plenty of power to run a game as dated as Q3. Heck, Q3 was running on Pocket PC's
with playable framerates several years ago.
2. Everything I've been able to gather on the version of Q3 running on the N900 [which is very little at this point] is that it's a port that's currently in development
. Regardless if it uses the original data files, the engine itself is custom... so at this point there's no telling what features may have been left out to provide a smooth playing experience. Also, keep in mind that Maemo
is a Debian derived OS written specifically for Phones/Internet Tablets. That combined with the fact that it's a custom port tells you it's not "the" linux version.