> but need to independently implement updates going forward.
That's not needed either? But since you've provided no rationale, it's hard to point out where the mistake lies.
What's wrong with using known code updates as long as you remove the anti-user parts?
Because you have no control over the future of the project. If Firefox or Chrome starts going down a route where they deprecate features you need you probably won't have the expertise to keep them going.
Anyway modern browsers are too hard to build profitably I guess without anti-consumer weirdness. Might have to switch to a cli RSS reader...
I guess if we really get technical we could say you can fork, but need to independently implement updates going forward.