One of the best ways to learn not only about a particular project but get a feel for the community that is working on it, is to subscribe to the mailing lists associated with that project. You may even be able to post your own ideas for the project as a way of introducing yourself to the project team. However, your ability to subscribe to project mailing lists depends on the project's licensing. Most open-source projects will allow you to subscribe before actually joining the project, depending upon the project owner's preference.
In the case of proprietary projects, you may need approval to join the project at the most basic "observer" level before you can subscribe to any mailing lists. You can read more about mailing lists here.