A couple weeks ago I posted about the Hamstersoft Ebook Converter. While the app may have been extremely popular, there was also a problem with it. The Hamstersoft Ebook Converter was based on code copied from calibre, only the Hamstersoft developers neglected to follow all the license requirements.
The issue has been resolved, so it doesn't really matter. But Hamstersoft were supposed have released a complete set of source code for their app; this was required under GPL. Hamstersoft did finally release the source code about a week ago.