Yeah, they were too, it seems; there a slide asking the author himself whether the code, the copyrights, the logos, or just what exactly was sold. No answer was provided.
As far as I understand it, things owned by the Bukkit team (i.e. servers, bukkit.org) and the rights to the code owned by the 4 core devs who were hired.
I wish people would tell you what's wrong with your comment instead of downvoting you into oblivion. Sorry, sometimes HN sucks.
There's a great difference between selling access to your software and selling your project itself, i.e. the copyright assigned to your code and/or logos, trademarks, etc.