(obviously taking its name from Maya), formerly The Mops, is a 3D modelling program written by Randolf Schultz. It's distributed under a BSDish license. It works under *NIX and also supposedly ("experimentally") under Windows.
Currently (version 1.1), it is fairly stable and works just fine.
Ayam is just a modelling program; it uses Renderman renderers to do the hard job. It works just fine with BMRT.
Ayam is yet another example of "Great program, bad toolkit" approach: at the moment Ayam works better than K-3D, but uses a pretty slick but pathetic toolkit, Tk. (Tk is tolerable; could use better file requesters though...) Tk's existence is justified, though - the scripting side of Ayam uses Tcl.
For this sort of program, Ayam is surprisingly easy to understand; I read the setup instructions, looked around a bit, experimented with the mouse, and found out that it was pretty easy to use. There's a toolbox, object hierarchy/properties box (that has the principal program menus); Wheel zooms, right mouse button is for changing viewpoints. I could create a simple test scene I wanted in no time! Though, I'm not a BMRT or Renderman expert, so some of the things were a bit complicated at first, but some guessing helped a lot...
All in all, a worthy thing to toy with while waiting for the stable releases of K-3D or the Return of the Grandson of Blender!...
Home page: http://www.ayam3d.org/