You're right about verification, there'd be a lag for changes until they become settled. Some projects do have moving targets - like youtube-dl - but testing is simple, and it's only one thing. (BTW even court tax rulings can have dissenting judges, so some points are real uncertain)

Many popular open source projects began as an open source version of something. e.g. linux. The structure of the software, to facilitate contribution, could break new ground.

I think the most significant and difficult-to-solve barrier is making contributing accessible to non-devs.