Tor browser uses the latest version of Firefox that they can verify their patches on. The developers need to verify the correctness of all patches and that ther

Tor browser uses the latest version of Firefox that they can verify their patches on. The developers need to verify the correctness of all patches and that there are no new ones needed. "Un-fork" in this context means "upstream", or get the patches that Tor browser uses into mainstream Firefox. The developers of Tor Browser will still always need to check that Firefox isn't doing anything improper and that privacy is maintained – but upstreaming the patches will make it a lot easier.