An Open Source version of the REDUCE algebra system
This system has a lot of convenient functionality; in my case for zeilberger manipulation. Actual errors found were fixed almost immediately! The interface Texmacs and CSL (native) could use some improvement but I guess I could do it myself if I was really bothered. As far as I can tell the zeilberger tools are more extensive than the other free algebra programs; although a few additional features would be nice. As before I should work on doing it myself.