Rated 4 out of 5 stars
Fix for beta users:
Ignore version check -> Save link as a xpi. Open the xpi file with 7Zip/WinRAR whatever. Then edit the install.rdf file. On the bottom there will be something like max version. Adjust it to 3.*.
Save the changes into the archive/xpi file. Open it with Firefox -> Voila! Compatibility check passed.
Works for every addon!!