I have just discovered a very wonderful tool for patching roms and isos under OS X:
MultiPatch. It handles IPS, UPS, PPF, XDelta or BSDiff, and it's a fine Cocoa Universal app!
Also, in the official bsnes forum I have found a Mac build of the 0.73 version (
this topic, 11th post). It has a ugly, and buggy!, QT interface, miles away from the shiny Bannister's Cocoa port, but it has all the feature of the original bsnes, such as the IPS/UPS support.