I don't know how many of you visit the MozillaZine forum thread for this extension, but just in case you haven't, please know that there is an update for Firefox 4+ available here: http://forums.mozillazine.org/viewtopic.php?p=10928615#p10928615
This version treats the permatab more like an App Tab, but keep in mind it is still very much a beta.
On that note, Permatabs Mod has been made available on GitHub for modification by the community. The source can be found at the GitHub page: https://github.com/deos/PermaTabs-Mod
We are sorry that this hasn't updated as much as we would have liked, but deos has had a hard time keeping up with it due to real life concerns (even with what help I can provide on the support front). He does what he can, but we could use all the help we can get (especially if you have experience writing Firefox extensions).
If you have an interest in seeing this extension stay alive, feel free to come on by the thread and help out; any assistance will be appreciated. Thanks.