Re:Maxima! (Score 2, Informative)

It's misleading to call Maxima a "continuation of Macsyma". In the early 1980's MIT Macsyma was forked into a public-domain version (DOE Maxima) and a commercial version (Macsyma). Maxima has had very little development since then, whereas the commercial version has had many significant enhancements, keeping it competitive with Mathematica and Maple. Unfortunately the commercial product is now in limbo since Macsyma Inc. went bankrupt a few years ago.

For further details see the newsgroup sci.math.symbolic

Disclaimer: I am one of the developers of Macsyma, both at MIT and later commercially.