I'm not sure OSX had even been released when v10.5 was out.
Your "orangutan" disc will also install A:M on a PC if you happen to have access to one. You can get the last update to v10.5 at the ftp page. I think 10.5r was the last one. Not sure if it was AM2002 or AM2003. The installer usually says what version it is doing.
10.5 was much improved over previous versions, but many bugs have been fixed and improvements made since then.