PANIC doesn't exist formally as a CGI right now, but it never was very formal. A limited form of "PANIC" can be enacted within the animated stutter of SLITHR -- http://sito.org/synergy/slithr -- granted, there are only five threads and there is no "branching" per se.
PANIC, to me, is more of an agreement to gather and create collaborative art "live". Thus... you can PANIC on Gridcosm, HyGrid or Slithr. There are security issues with FTP that we haven't had time to work out yet. My plan has been to modify the Slithr scripts to allow for a more "open" image-series-style PANIC.