Since the drive does no longer come with Twonky the installation of the latest version of that media server will require getting a license.
There are several articles on the community that talk about issues with Panasonic TV’s and the ability of playing MKV files.
http://community.wd.com/t5/My-Book-Live/mkv-movies-on-DLNA-Server-MBL-3T/td-p/605341
http://community.wd.com/t5/My-Book-Live/WD-DLNA-server-mkv-to-Panasonic-TV/td-p/587661
