If you'd like to avoid this extraction, you can fork their command line client code (along with the open source headscale server) and run a mesh network across your linux machines with all the magic DNS and userspace-TCP/IP-stack goodness that you're used to. Tailscale has given away a lot of the engineering for free.
However, as soon as your fork becomes incompatible with Tailscale's stack, you lose a massive value-add: proprietary platform support. Today, you can add the sale's guy's iPhone to your tailnet in seconds. If Apple's capricious automated AppStore security pulls the Tailscale app from the AppStore, Tailscale Corp is big enough to get Apple's attention. A small FLOSS group with some forked clients on github won't be able to provide this same operational stability.