It sounds like their idea of open source is something along the lines of "slap a MIT license on it, throw it over fence, and hope random nerds on the internet finish it while we wait idly."
Until someone with a larger budget than you forks it and uses their immense resources to force you out of the market. Then you liquidate your company and someone else gets the rights to maintain your fork.
Here's one I'm sure about: no one cares about Mathematica except a couple of schools, professors, and finance wonks who've clung to it since the early days of CAS. The language is wacky enough that no mainstream user would prefer it (even with all of its built-ins) over Matlab or scipy. And I say this as someone that has developed things in Mathematica.
(Plus, I think putting Stephen Wolfram at the top of a Linux kernel-type project is unlikely to work well at all.)