Do you mean "still only maintained by the one" Or just that the originator still participates? If the former, I don't really think there are any. If the latter

Do you mean "still only maintained by the one" Or just that the originator still participates? If the former, I don't really think there are any. If the latter, there are tons of examples ranging from Dropbox to Facebook. The "still only" is almost antithetical to anything beyond very small scale success.