At this point, working on FF seems a very good choice 
For anyone looking for something else than coding (or on top of it), you can also contribute to “human-connectivity”, localization: app translations and keyboard layouts in your language (or any other language you know well). Without them, L5 is handicapped as a communications device as users have a hard time connecting (passing on information in the correct and understandable format and manner) with peoples in other cultures. Or, if you do code something, make sure to put your app available for translations (a free tool / site like Zanata or Transifex IMHO preferred).