> I legally can't take part. I have a job now, which
    > claims ownership over any tech-related IP I create
    > ... This is true for nearly anyone with a standard
    > SV job.

For the majority of (admittedly non-SV) employment contracts I've read, most will limit it to work that is linked to your employment only. In the few cases as a developer and recruiter where that's not been the case, I've had no trouble at all getting the company to sign-off on a clause that limits it to that. Legal is much much much more worried that you'll rip off actual company IP or technologies that you've built in the workplace than that you'll discover cold fusion in your garage and they won't get their cut.