As a general rule, there are several steps to becoming a contributor for a project of this magnitude. There's a long gestation period that starts with learning the structure of the project and the source very well. As your contributions to the discussion become more pointed and show evidence of understanding, you may be invited to take a more active role. The existing contributors to a project like this, however, are wary of individuals who would like a prominent role but require more resources to support than they offer. Please be mindful of this when you approach a contributor or committer -- their time is valuable and quite limited.
If you want a freer hand to add things with GlassFish, consider writing a plug-in. It's a very good idea to have some community support before you go about writing one. There's no rule that says the community has to like your proposal, but if some number of people see the need your proposal can fill, you'll find a more eager bank of testers when you're ready for them.
Make visible what, without you, might perhaps never have been seen. - Robert Bresson