You can get it from dotPlant SVN on Google Code page.
Later I'm planning to migrate sources to GIT repository at assembla, because I'm thinking it's fork feature will boost the process of developing.
If you can't find SQL dump - please, don't mail me. I've already lost it, because I'm making a new branch of dotPlant called Cockatoo. So you are welcome to do everything you want with the current source code.