I have OSX 10.9. Used 2nd link above. Copied Electrum.app out of dmg to Applications, tried to open, got:
Electrum.app is damaged and cant be opened. You should move it to the Trash.
Firefox.app downloaded this file today at 14:51.
Repeated steps above, same error.
Tried to open within dmg as well, said it was damaged too.
ETA: OSX lies about it being damaged on first run if you don't have this set:
Change System Preferences: Security & Privacy: General: Allow applications downloaded from: Anywhere.