This is a maintenance release that fixes several issues found in Pellet 2.2.1. Complete set of tickets closed for this release are listed at the Trac page.
We’ve also updated the Pellet Reasoner Plug-ins for Protege 4.0 and 4.1 to use Pellet 2.2.2. You should get a notification next time you start Protege.
A note for Protege 4.1 users: you will only get the update, if you are using the most recent version of Protege (i.e., 4.1 beta). We do not plan more Pellet plugin updates for older versions of Protege 4.1.