Any possibility of making a pay-to-use Firefox extension?
SwellJoe: I (actually mostly a contractor, though I ended up maintaining it) built a toolbar back in the neolithic era (Firefox pre-1.0) for managing a URL black/white list for a product I was developing at the time.  We gave users a username and password (the same one they used on the website version of the tool), and they simply logged in.  Anybody could download it, but it didn't do anything useful if they weren't logged in.