This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
I have developed a small adapter which lets you plug a PS/2 mouse (mechanical, optical, cordless, etc. as used with IBM PC-compatibles) into an Apple mouse port. It works with the mouse port on the AppleMouse card and the built-in mouse ports of the Apple IIc, IIc+, and Laser 128. (It should also work with older Macintosh models (128K, 512K, Plus); but, I don't have one to test it on.) The adapter, which was demonstrated at KFest 2003, has a pair of microcontrollers which translate the PS/2 protocol into the Apple mouse format. No software changes or drivers are needed on the Apple side. I've set up a web site with pics and info for selling the adapter via PayPal at ... http://vintageware.orcon.net.nz/ . By: Roger Johnstone