While I'm not the best at reading the raw Java output, the one that you have presented us has no errors per say in it. It does indicate towards the end after you've actually loaded a word that the system is overloaded. Allocating more memory to Minecraft through the launcher options(if they ever actually got that to work properly) would probably help with that. It also does show that for one reason or another that it isn't launching as modded.
Here are a couple tips that seem to clear up quite a few problems. First of all, how are you actually running the launcher? Are you double clicking on it or executing it from command line? I've had very good success on the *nix systems that I have tested including OS X by running the launcher by command line(java -jar FTB_Launcher.jar). Also, you might try putting the launcher in a new folder that you created and running it from with in there. To run it from command line you would open terminal found under Applications -> Utilities -> Terminal then execute the commands.
Code:
$ cd /Users/Oliver/Downloads/
$ java -jar FTB_Launcher.jar
That is provided that you haven't changed the name of the launcher or where you've placed it. If you put the launcher in a new folder, be sure to use the right path to cd to. Macintosh HD is the first / in the command line. So starting with that, it would be /path/to/where/your/launcher/is/
I hope that this has been some help and that I didn't just explain all this basic Unix command line stuff for nothing
You may also want to see these posts if you experience the launcher crashing:
http://forum.feed-the-beast.com/index.php?threads/fix-for-launcher-with-launch-command-file.1019/
http://forum.feed-the-beast.com/ind...her-on-mac-minecraft-crashes-immediately.892/
