But the secret of open source is that it was the same people (or at least the same job roles) who were previously writing proprietary software. Companies just decided that it made more sense to have them collectively, collaboratively work in public on infrastructure software than to pay a single vendor for closed-source code. It's not that hobbyists are implementing core OS scheduling primitives like cgroups, it's that the professional engineers doing that are now employed directly by end users like Facebook or Google instead of by vendors like SCO or Sun.