Here's a possible solution. Do it anyway, knowing that if your company really wants to piss you off by making an issue out of it, you can (and will) tell them to piss off and quit. No job is worth sacrificing your personal life and freedom for.

When they make a problem, and you quit, if you've got someone in the company that values your contribution enough to fight for you and find a compromise to get your OSS contributions back-approved or whatever, great. The employer will benefit from the loyalty you will feel towards the person who solved the problem ("the greatest boss evar"). If your boss can't make the problem disappear, then you quit. If you've organised your life correctly, you can afford a few months of job search, and your OSS contributions are a testament to the quality of your work.

(Not saying that I ever did this. And you should probably not cross-reference "git log" with my CV either.)