From the original list announcement:
I am very pleased to announce the eMir project. eMir is starting out as a fork of Canonical's Mir display server. We were all excited to see someone doing something about the stagnant display server situation, but there are several problems with a Mir project run by Canonical. eMir, or enhanced Mir, aims to be real successor to the dated Linux graphics stack that everyone can contribute to and use.
We all dream of using high-quality mobile and embedded devices running Linux, using a full GNU/fd.o stack. However, consumer demand for fast'n'fluid multi-touch interfaces make this impossible; no such device will ever exist if it needs to run on an X server.
Canonical recently excited and energised the Free and Open Source Software community with the launch of Mir, a next-generation display server for modern GPUs and SoCs. (Canonical is the parent company of Ubuntu, the world's most popular distro.) It finally looked like we were going to get a modern graphics server that would actually be ready this century. Mir already released version 0.0.2 last February and is still surging ahead.
Wayland had a long time to release something finished, even to give us a sign of progress. The only reason we've seen recent news coverage of Wayland activity is because of the challenge posed by Mir. Recent forking of this project just shows how divided the developer community is. We need something that will work, soon, with a mature and stable developer community behind it.
After the euphoria died down, it became clear that Mir is beset by several problems. Copyright assignment, strong resistance from hold-outs, forcing developers to use Launchpad and general lack of vision necessitated a fork. eMir will have several benefits over Mir:
As the obvious successor to Mir, we expect most activity to be behind our project. All future progress will be made here.
Either way, interested contributors need not worry about cross-posting patches to Mir lists. All our changes will be available in a publicly-available repo on GitHub, which the Mir team can just pull from when they need to.
Come join in at http://github.com/eMir-server/eMir !