It was closed because he posted it in the wrong section. I think the mod should have probobly moved it instead though...
Anyway, the nebula team's model 2 emulator and the one in MAME are the only ones I know of. And MAME is the only emulator I know of for Model 3, although I have no idea how much it emulates, if anything. The problem with emulating the Model 2/3 systems is that there is a serious lack of documentation avalible on the hardware, so a lot has had to be reverse engineered. On top of that, since they're arcade hardware not that many people interested in reverse engineering them can even get ahold of them. Model 2/3 emulation will progress as long as people have the desire to keep working on it, but at the moment there aren't a lot of options.