[rz2k]

I believe that Sage was modeled after Magma, which isn't important, but I highly recommend this long blog post by William Stein[1] talking about his motivations, the problem of basing academic work on closed source software, and in the case of Magma, the potential politics of even being able to get the software.

[1] http://sagemath.blogspot.com/2009/12/mathematical-software-a...

[lutusp]

I agree, I've read that piece, it's very worthwhile, especially with regard to the issue of being able to publish the mathematical methods built into common math environments.

Oh -- my Sage tutorial: http://arachnoid.com/sage