Hello dear Anthony,
Don't worry, Linphone is not dead at all, it's actually very much alive.
We're a team of 8 good people maintaining the project, and although we sometimes take long to answer on the mailing list, we're there.
As Charles told you, we just released a new website and Linphone 3.7 is not even a few months old. iOS version is totally fresh and Android is coming.
So don't worry!
Was it something we didn't answer you in the first place that made you think this?