Jo wrote an entire blogpost about it:

https://blog.prusa3d.com/the-state-of-open-source-in-3d-prin...

One of the big takeaways from this for me is that Jo doesn't really understand IP law. He talks about wanting a new license for open source hardware; the trouble with that is that a copyright license does not and cannot protect a hardware design. That's what patents do.

That's not a defense of current IP law, just a statement on the reality of what it is.