There it is, Firefox Version 3.6. And personas do work too. After you installed them.
You get the sources of version 3.6.0 at ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/3.6/source/. You need to download ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/3.6/source/firefox-3.6.source.tar.bz2 (perhaps you need a right-click here to get it).
The sources are compiled as I described in Firefox 3.6.x Community Build for PowerPC Linux.
If you prefer to use the binary, it's here: firefox-3.6.en-US.linux-powerpc.tar.bz2
Because the Firefox 3.6 runs as good as version 3.5.x, I stop compiling the 3.5.x version any more.
If you need information on how to use the binary, please refer to Firefox 3.6.x Community Build for PowerPC Linux.