Hudson's SCM is just converted from CVS to Subversion
When I first created Hudson on java.net, java.net only had CVS and no Subversion. Since then, java.net had added the Subversion support so that new projects can choose to use Subversion, but the existing projects didn't really have any viable migration path.
Some time after that, this got the attention of the java.net team, and a document has been written to explain how to migrate. Unfortunately, the catch is that you have to pay a fee to do this, and I couldn't convince myself to pay $500 (or so) myself to do this, so I left it there.
As Subversion steadily replaces CVS everywhere, however, it was just a matter of time before this issue gets revisited, and that happened a couple of weeks back. Tom Huybrechts brought this up again, and I replied that "yes, we tried, and we need to do some fund raising to do this." That was when a little miracle happened. See, collab.net is now apparently using Hudson, and one of their developers, Adam Ambrose, was in the Hudson dev list. He kindly talked about this inside Collab.net, and as a result, they graciously agreed to do the conversion for free for us. How nice of them!
So this morning, I was happy to find a new Subversion repository for Hudson. I still have to make adjustments to release scripts, but documents on Wiki are already updated to reflect this change. For those of you who have Hudson source code checked out, see this document for how to do it now,