Marcus Overhagen was threatened by yellowTAB recently over an apparent NDA issue. On his blog he states what has happened, the original email (in German) he received from yellowTAB, and more interesting details.

I will at this time not take sides on this issue as I do not have enough information at hand to do so, but what I will do is allow you to follow the saga and read as much as I have. Please take a moment to read Marcus's blog and consider leaving a comment if you want.

OSNews.com also has coverage, with many comments already posted for your reading pleasure.