Do you already have OSX installed, or have the OSX installation discs? OSX should be able to run the older software under an OS9 emulation that's built right in to OSX. The emulation can be made to be visible (so that users actually wind up seeing an OS9 interface when they run an older program), or it can be made to run "in the background" so that the software runs, but the OSX interface is what they see.
The emulation is also supposed to start automatically - without any input from the user - when an older software program is opened that requires OS9 to run it. What should happen in that case is that the OS9 emulation starts up (essentially, it boots up in the same way that it would if you were starting up a computer that ran OS9, but it all happens withinn OSX). After OS9 boots, then the program should run. The whole OS9 boot-up can be made to run at OSX's startup, so that there is little delay when an older program is run...otherwise you have to wait for the OS9 boot-up to finish inside the emulation).