In principle, the team consists of just one person. But a huge number of people have helped in numerous ways. Some of them may not even be aware of this fact, but still deserve credit. And many have likely been forgotten, completely unintentionally. It's a wiki, you can change it. 
Design:
- Arnd Bergmann - A major influence all over the place. There is hardly any part of the design he wasn't part of.
- Martin Schidefsky - GC was designed during a bushwalk with Martin and Arnd.
- Dirk Bolte - Hugely influenced the level design.
- Mendel Rosenblum, John K. Ousterhout - Designed sprite lfs, from which many ideas were taken.
- David Woodhouse - Suggested the wandering tree.
- Artem Bityutskiy - Suggested only compressing leaf nodes.
- ??? - someone else at LCA2007 suggested the same
- Neil Brown - Explained problems with telldir/seekdir, nfs and rm -r.
Marshall Kirk McKusick - Did soft updates for BSD, I will use something similar for LogFS.
- Uwe Schmidt - Suggested simple revert-to-snapshot
- Jörn Engel
Documentation:
- Robert Mertens - Worked on every paper/presentation so far
- Dirk Bolte - Vastly helped on the GC presentation
- Jörn Engel
Testing:
- Arnd Bergmann - I still have to dust off his testcases. Shame on me.
- Jörn Engel
Development:
- Jörn Engel