I've been playing with for a while but I do not think it will work with GB.
In fact I went to the website
http://www.essej.net/sooperlooper/features.html
And I dl'd sooperlooper. Then I installed it and couldn't get it to work. The documentation says multichannel which will not work in GB.
So I went to the SooperLooper forum link to find out.
Under general discussions/ looping techniques you'll find real info about sooperlooper BUT under all the other forum topics like "MIDI Setup", "AU Lab", "Mac Specific Troubleshooting" (to name just a few of the dozen there) you will not find forum questions but links to pictures of ****. These links are in all the other forum topics.
I have never seen anything like this before in an AU forum.
So something is not right one way or the other.