How does this compare to other OSS like zrok?

It looks like there might be some overlap. There are a bunch of solutions in this space! It looks like they do provide public access to resources which is what Pangolin does. We might have a bit more of authentication options but dont hold me to that.

We are working on some "client" based solutions as well similar maybe to what Zrok is doing which we may release in Beta in the next couple of weeks!