I recommend you to use version 1.24 if you want to play online.
Here you can download a pack including Jazz Jackrabbit 2 versions 1.23 and 1.24 (TSF), JCS, the JJ2+ addon and BigJazz.exe (for a higher resolution in 1.23).
Download Jazz Jackrabbit 2 OEM version 1.00h here!
Jazz Jackrabbit 2 for mac
This version of Jazz Jackrabbit 2 is made for MAC OS / OS X
JJ1 on PSP
Download JazzJackrabbit on your PlayStationPortable!