"This program is not developed anymore and is only provided for compatibility. Use avconv instead."
Five minutes googling and I realized there had been a (somewhat acrimonious) fork. So my interpretation was quite natural: the libav developers and/or the Ubuntu maintainers were being dicks to the original project. If they really wanted to be clear they could have said something like:
"This is a deprecated wrapper around avconv, part of libav. It is not part of the ffmpeg project. See <url> for details."
How hard would that have been?