You can ask questions and post comments on the MacHg mailing list. As things have developed a lot of discussions have gone on within the bug reports on bitbucket. However these are not as searchable as the google group messages. Thus in general it would be nice to move these discussions to the google groups messages, if possible.
Commercial Support (MacHg)
Primarily MacHg is an open source product that I am trying to create for the benefit of Mercurial users on OSX everywhere. I created and develop MacHg for the fun of it. I am flexible about adding specific features that you need for MacHg which may not be useful to the wider community. More generally if some company wants to provide sponsorship for some desired features that I am already planning that would also be fantastic!
Commercial Support (core Mercurial)
Although Mercurial is open source software there are a number of organizations which do commercial support of core Mercurial and consulting involving Mercurial. Personally, I have interacted with Martin Geisler on Mercurial issues on many occasions and he has always been very friendly and extremely knowledgeable. In addition he is one of the crew members for Mercurial. You can contact his consulting company here:
aragost Trifork consults in everything Mercurial. We can help you with installation, continuous build integration, customizing your workflow, training, extension writing, remote repository troubleshooting, and any other support issues involving revision control. Please contact us to discuss how we can craft the best solution for you.