Me:

...

I relaunched Demo.app with a doubleclick, but instead of the Demo.app launching, HotConsole launched.

I quit, trashed the Demo.app, ran the rakefile again, but Demo.app continues to launch as HotConsole.

Laurent:

I wasn't able to reproduce this strange issue... if you can still do it could you archive the directory and send it to us? My fault. I altered the directory path to Developer/Examples/Ruby/ MacRuby/HotCocoa/demo, which caused the muck. Restoring the directory path fixed it. (And changing the path in the same fashion caused the problem to recur, so I know not to do that again.) Thank you.