also to follow on the "why not use tailscale" should be because they're a business who seeks to make money and we are fools to keep concentrating distributed technology to a handful of centralized owners (!)
especially when iroh makes it so easy and awesome to do it right.
So instead of paying a subscription fee to Tailscale to support your distributed application, you pay a subscription fee to Iroh to support your distributed application. (https://www.iroh.computer/pricing says $19/month for what most people will want to use it for).
Either one will allow you to stop "concentrating distributed technology to a handful of centralized owners", but the "why not use tailscale" part of what you're trying to say is not at all evident from your comment.
But headscale is a community project. The iroh relay code is by number0 just like iroh itself and lives in the same MIT and Apache2 licensed repository. You can even embed it into your webserver if you have a special use case - it is very modular.
especially when iroh makes it so easy and awesome to do it right.