Anyone can contribute to Apache Flex: Translation, Design, Documentation, code - whatever you think matters. Persons that can change things are called a "commiter".
Non-commiters have just to take two, small, hurdles to become a commiter:
You can contribute whatever you like. Use the mailing-list or Jira and request if your contribution is interesting to Flex. The chances are high that good things will be taken immediately.
To become trusted all you need to do is getting voted in by the team. Make yourself a little known and ask the mailing list to become a commiter. Unless you insult people it shouldn't be a problem.
Don't hesitate - we are waiting for your contribution.