Ask HN: When do governments allow export of cryptography software?

I see this notice in the TextSecure README:

   The U.S. Government Department of Commerce, Bureau of
   Industry and Security (BIS), has classified this software
   as Export Commodity Control Number (ECCN) 5D002.C.1, 
   which includes information security software using or 
   performing cryptographic functions with asymmetric 
   algorithms. The form and manner of this distribution 
   makes it eligible for export under the License Exception 
   ENC Technology Software Unrestricted (TSU) exception (see
   the BIS Export Administration Regulations, Section 
   740.13) for both object code and source code.

huh? Why does the US Govt feel this software is "eligible for export"?

Does that mean it has a circumvention available?

TextSecure is just an example. More generally, on what basis do govts allow export of encryption software?