Xouvert is a more public development branch. Not only do we want to maintain compatablity with the Standard X11 protocol, but we also what to have our work reintegrated and recontributed back into the XFree86 project. There are are alot of good things about XFree86, like its production quality stablity, and we don't want to reinvent the wheel.
2.2) If Xouvert is not a fork then what is a branch?

We want to have a our work reintegrated and recontributed back into XFree86, so we want to maintain code and license compatablity. A fork would mean a complete severing from the XFree86 project, we just want more open, organised place where can do work on X. Think of a tree, a fork would be a competeing vertical trunk; where as a branch grows outword, but in the end helps the main trunk grow.
2.3) So why are you branching from from XFree86?

We just want more open, organised place where can do experimental work on X. We are branching it to pick up the pace, so that we have an organised infrastructure to do this development work and to provide a product for those who want to live on the bleeding edge.