Like others have said, use your time to learn new things at work.
And I agree your company likely has no grounds to your IP but what might give them some ground is if you're either caught working on your project at work or if your performance slips to the point they think you have somehow used your time for other means.
I think OpenBSD should reach out directly to manufacturers of the many hardware platforms they support (HP, SPARC (now Oracle), etc) and ask for donations. Of course, only the companies that are still in business.
And I agree your company likely has no grounds to your IP but what might give them some ground is if you're either caught working on your project at work or if your performance slips to the point they think you have somehow used your time for other means.