In theory, maybe. But, let's say you want to go maintain X11/GCC/Qt (or even xterm), I doubt "anyone" can. Some people are full time developers on these project

In theory, maybe. But, let's say you want to go maintain X11/GCC/Qt (or even xterm), I doubt "anyone" can. Some people are full time developers on these projects, paid by some company we somehow rely on. You cannot just replace an expert working on such a big piece of software. Of course, using free software might widen your "trusted base" compared to the situation where you go full MS.