There are currently two different downloads for OSX, one is named osx, while the other one is named osx-jaguar

The reason for this is that Apple added more functionality to 10.3 and to make use of that, it will no longer run on OSX 10.2 (codenamed Jaguar). To make the game useable on Jaguar, then a special download is available, but it will miss the bugfixes/features, that relies on newer functionality.

The general download is a universal binary and should work great on all macs using 10.3.9 or newer, no matter what processor it got. You should at all time avoid the Jaguar Build if possible.

Technically the universal binary is a triple binary because it contains code for 3 CPUs and the CPUs in question are PPC (G3+G4), G5 and Intel. The Jaguar build is only optimised for PPC and other (newer) CPUs will not benefit so much from their advanced features. This is another reason to avoid the Jaguar build. It's generally slower on modern CPUs.

Current list of missing features in the Jaguar build:
-Can't save screenshots or savegames if certain chars are in the filename. This mainly applies to European chars and hits German hard as the month Mär (Mar) can't be saved