I have published the source code that I demonstrated during my 360|Flex presentation on github. You don't need git to get the source, just click the download button on the page. Again, this is the code for Improving your Programming by Reading the Flex Source Code.
This does not include the class browser. That is an AIR project that I will publish separately.
Github is a source repository system like Google code or Sourceforge, but using git - a distributed source control solution. I recommend git, if you haven't used it, for any side projects or open source projects that you work on. Git allows anyone to branch/fork a project and make any changes they see fit. Then the changes can be merged back in if they are useful. Github supports forking of open source projects so people can, for example, make changes to a project available without needing approval of the original maintainers.