Question: why would anyone Sage > Magma (even though it's now a company. i.e. since there already is a clear and ahead forerunner?)
TL;DR: Researcher A finds things he wants improved in Magma (closed source) but can't. Researcher B tries to write improved FOSS implementation, but lost his job, likely in part by spending too much time writing said code and not doing other things like writing papers. Researcher A moves on and has a successful academic career. Moral: writing FOSS can cost you your academic job; it's safer to find something else to do.