The Lempel-Ziv algorithm that compress is reliant upon is not entirely free of encumbering patents as I understand it. RedHat's zeal with GPL or die sometimes gets in the way. It might still be on the install CDs just not default installed any longer, otherwise rpmfind.net, and then dead last you can just do a
www.google.com/linux search for the source, try searching by zcat as compress will pull up a lot of garbage.
Luck,
Finegan