Maybe they should treat it as a side project, and not as a job. When people treat open source projects as their day job everybody loses.
That's a new one. How does someone getting making a living while developing open source software mean "everybody loses"?
You can, however, do it as a function of your work for your employer. Almost all of today's viable FOSS started like this, because it provides the financial security and moral support you need to bring a FOSS to maturity.