A new bug was filed here:

http://bugs.freepascal.org/view.php?id=25339

Summary:

When attempting to build and run Lazarus from trunk sources (and going back quite a few revisions), the IDE always hangs as the Source Editor window is displayed. Lazarus can only exited at this point and cannot run any further.

I am able to successfully build and run the Lazarus IDE from a revision created in September 2013, so something was introduced to cause this behavior.

Tested on Mac OS X 10.9 (Mavericks)
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