So what are DAMs actually? Maybe this short introduction video of the system mentioned above, will give you an idea quickly:
TACTIC from TACTIC on Vimeo.
The system was quite recently open-sourced under the Eclipse Public License, and has been previously in use by some of the big 3D gaming companies. For an overview of the features head here. Its client interface is completely web-based, and you can easily set up your own asset-repository VM server if you want.
For most FOSS games (which tend to be mostly one-man shows :( ) such a system is probably overkill, but using a DAM might actually help involving more people and make collaboration across the globe more efficient (Just like GIT and such systems did for code collaboration projects).
Maybe someone would also be willing to host such a service for FOSS game projects? However high data-transfers rates would make it probably not possible to offer such a service for free. Feel free to comment on that too ;)