There is no "app" or "program" for Tomboy. You have to build it yourself, using XCode (make sure you download the right version), MacPorts (make sure you download the right version), "Git" (yeah, introduce yourself to that little gem).
Tomboy is supposed to be a list manager. All this work? For the ability to WRITE LISTS? I have spent hours screwing around with this Tomboy project, and it still did not build.
STOP! Do not give me stupid advice about how I can spend even more of my time to build this thing successfully. I believe that the software should work for me, and I should not have to work for the software. Tomboy is a waste of time for 99.9% of computer users.