It is intentional that there is no "delete project" feature. Projects are to be used for building stuff. Then, when they are done, the production files are released via the RTA Uploader (I know, a bad name), where they are placed into the Resources, Tools, or Addons sections. The project pages are left as an archive of progress.
It is amusing that many people look for a "delete project" feature, when I never see anyone request such a thing for forum topics.
Hmm. I should make a feature where you can "disown" the project, where someone else could take it over.