There is a separate page detailing how to be a developer on the Mercurial.Net project.
It can be found here: Developer
Starting with version 2.0 of Mercurial.Net, CodePlex will host a clone of the stable repository. Anything pushed to CodePlex, even though the stable branch inside the repository will be discontinued, should be considered stable, and tested.
Development will be hosted on Fogbugz
on demand, hosted by Fogcreek Software
You can find the raw unstable repositories here: https://mercurialnet.kilnhg.com
CodePlex has an issue tracker, but any issues reported to it will be mirrored into the Fogbugz on demand issue tracker, as it is superior to the one here on CodePlex. A link from the CodePlex issue will be added to the Fogbugz one.
To view the Fogbugz issue tracker you have to register a community user.
You can reach the Fogbugz issue tracker here: https://mercurialnet.fogbugz.com