As for you questions:
1. Always use mercurial checkout when consulting code. The link above is to old cvs repo that was not updated for quite some time.
2. win32 condition variables - it will be nice to use native ones but this is not the goal of the project. I would not put too much efforts on this at that stage.
3. There is no need to have 'full grasp' of mutex internals in order to use it. package.d is a place to consult for the usage.