Haven't seen any hacks to get CAPTURE working under OS X, but you can get video OUT working, it just takes some effort. (It requires setting up a VNC server on the computer, and turning it on with only a TV plugged in, then VNCing in and going to the 'Display' system preference to enable the display.) I haven't tried it personally (I do have a beige hooked up to a TV as its sole display, but it's running OS 9, and isn't on my network, so I can't easily VNC in to it,) but I've heard that's how you get it to work.
(Maybe this weekend I'll hook it up to the network and see if I can get it to work.)
heh. If "this weekend" meant "a year and four months from now", then I guess I was right. I finally got around to testing it.
So, yeah, you have to install a VNC server that automatically loads (I used osxvnc,) then turn the computer on with ONLY a TV attached, nothing on the internal video. (This also does *NOT* work if you even have a PCI video card in the system.)
You then have to wait for it to boot (with nothing on the TV, of course.) Then VNC in, go to System Prefs, Displays, and pick one of the resolutions that has "(NTSC)" or "(PAL)" on the end. (Mine is ONLY showing NTSC resolutions, I'm not sure if that's because I had NTSC picked in OS 9 or what.)
In my case, I also had to un-check "Show modes recommended by display", because I'm running 10.1.5 on this machine.
Now I can take it off the network, put it back on the TV in the living room (I'm actually testing it on the RCA input jack of an old Blue & White Apple Studio Dislpay, while VNCing in from a Blue & White G3 plugged into the VGA port of the display!) Of course, I'm not entirely sure what I'll do with it in the living room, either. My wife doesn't use it for guitar lessons any more, and without network access, it can't be a TV internet machine (the Wii does that, anyway.)
Maybe I won't bother putting it back in the living room, after all.