Sadly closing the site off to external access accomplishes nothing. They have proved untrustworthy, and will simply reopen or release elsewhere. Every time they post a binary, they need to post their source. That is the license.
It is unfair to the FBA Team, Dave (the original FinalBurn author), the MAME Team, external contributors, and previous team members for them to take everybody else's hard work, and use it in their own build, without then following the terms of the license.
I would still like to see them follow the license, and for the source code to their last binary released, as well as the source code to any future binaries, released at the same time as the binary.