FAS - The Open Account System
FAS is designed around an open architecture. Unlike the traditional account systems where a single admin or group of admins decide who gets to be in what group, FAS is completely designed to be self operating per team. Every group is given at least one administrator who can then approve other people in the group. Also, unlike traditional account systems. FAS allows people to apply for the groups they want to be in. This paradigm is interesting as it allows anyone to find out who is in what groups and contact them. This openness is brought over from the same philosophies that make Open Source popular.
People shouldn't assume that by applying for a group that they're then in that group. Consider it like applying for another job. It often takes time. For best odds of success, learn about the group you're applying for and get to know someone in the group. Find someone with sponsor or admin access and ask them if they'd have time to mentor you. Plan on spending at least a few days learning about the group, doing a mundane task, participating on the mailing list. Sometimes this process can take weeks depending on the group. It's best to know you will get sponsored before you apply.
Users, Sponsors, Administrators
Once you're in the group, you're in the group. Sponsorship and Administrators typically have special access in the group in questions. Some groups consider sponsorship level to be of a higher involvement, partial ownership of the group for example. But as far as the account system goes the distinction is easy. Sponsors can approve new users and make people into sponsors. They cannot, however, downgrade or remove other sponsors. They also cannot change administrators in any way. Administrators can do anything to anyone in the group.