Can you release MacHg for OSX 10.5 or earlier?
I am really sorry, but to the best of my knowledge the answer is it's just not possible...
This was a decision I took when writing MacHg in order to be able to use all the new cool modern stuff like GrandCentralDispatch which Apple introduced in SnowLeopard OSX10.6. GrandCentralDispatch allows one to easily do threading and manage thread pools. This leads to one of the things that makes MacHg so fast (or at least seem so fast from the user perspective): the UI doesn't freeze when it's doing background stuff. So MacHg is rather fundamentally wedded to 10.6. I also thought that it would be mostly developer types that need to use MacHg, and most of them should be on 10.6 as it is. Also, 10.6 has been out now since August 28, 2009 which is a while ago in terms of development time.
But in conclusion, I am really sorry that I can't release a version for 10.5.