Please note that all these development resources originally deployed on port 8000 have been moved to port 80 (i.e.
http://svn.modxcms.com/) to avoid access problems on some very particular corporate networks. If you have checked out MODx from SVN, you will need to perform an svn switch with the --relocate option to change the repository location for your working copy, or you will not be able to get updates, etc.
The URLs have been updated in the original post to reflect the change. Let us know if you experience any problems accessing any of the resources.