Something has happened with gcube being opened sourced. Some of its features have been ported to dolphin. Although it hasn't been released since that has happened. Plus emulation is a tough thing, so if you're sitting out there looking for some source to work on you're going to want to work with the best source you can get your hands on. Which everyone knows is dolphin, so it's possible some people are waiting on dolphin, which has been promising to go opened source off an on for well over a year now.
Of course it's all irrelavent to me as I don't see any downside to releasing source. Worst case is nothing happens with the source (which I admit is rather likely). But who cares if nothing happens, all that is lost is the 5 mins it would take to compress and post the source code.
Of course for the purposes of this topic they were refering to releasing the source for the plugins, not the emulator. Plugins have a little more chance of getting people working on them since they deal with a certain area and you don't have to worry so much about everything else.