CM10.1 is an open source replacement ROM for the Android phones and tablets. It looks and feel very much like stock Android and is much faster than the stock factory firmware. Cyanogen Mod 10.1, popularly known as CM10.1 is out for the Samsung Galaxy Tab 8.9 and almost everything is working, including GSM calls. Of course, to flash it, you must have Clock Work Mod recovery installed for the Tab 8.9.
List of working things.
3G (including GSM calls)