Today I violated the Mathematica license agreement in front of Eric Weisstein (a famous Mathematica developer), I talked with the developers of Wiris (rhymes with virus) which is a commercial competitor to the Sage notebook, discussed Mupad with a longtime Mupad developer, and gave away $1000 of tutorials, DVD's, and other goodies at the Sage AMS exhibit booth.
Eric Weisstein -- who told us that he is now an official Mathematica developer (doing graph theory among other things) in addition to his "Math World" came over to the Sage booth and asked a lot of pointed questions about Sage, mostly "how does this get funded?" We ended up talking for about an hour. There are numerous people at Mathematica who are well aware of Sage, and he claims he doesn't see Sage as a threat to Mathematica as a company. He said Mathematica has had a recent explosion in hiring as a result of greatly increased sales because of the new "Demonstrations" feature in Mathematica 6. We also talked a lot about graph theory and how Sage has a complete implementation of graph isomorphism testing, etc., which greatly impressed him (thanks Robert Miller!). Jason Grout asked about the Mathematica end use license agreement and Eric pleaded IANAL and I demonstrated using Mathematica via the Sage notebook -- all locally over localhost on a machine with a valid Mathematica license -- that this violates the Mathematica license. He got annoyed when I did a Mathematica graph through the Sage notebook... Later Eric talked about how he "hoped" Sage would continue to have momentum and not just die like other free projects. He gave Maxima as an example of a dead project, and seemed quite shocked when I mentioned that they are very much alive and have regular releases, etc. He then said that there is no such thing as free.
I met somebody from MuPad who has worked on that closed source project for a decade. They used to be a German national government funded project, then had an academic research branch until one year ago, and now are 100% commercial and private. I asked about their vision for the next 5 years, and he said "MuPad will survive", and said they were mainly happy to be stable. They also mentioned wanting to do more numerical and applied functionality.
I talked with a Unix guy who works on some Scientific Workplace. There is only a Windows version, and he is working on doing an OS X/Linux port, which they will finish "in the future"!
And that's just a little of what happened today...