I read it at the time you posted it is subject to export restrictions and it is not relesased under the GPL.
Code:
2. GRANT OF LICENSE.
BraveTree grants you the right to use the Software in accordance with the terms of this Agreement. You may load the software into RAM as well as install it on a hard disk or other storage device. You may not modify, translate, disassemble, reverse engineer, decompile, or create derivative works based upon the Software. You agree that the Software will not be shipped, transferred, or exported into any country in violation of the U.S. Export Administration Act and that you will not utilize the Software in violation of any applicable law.
In case you have never noticed there are non-us repositories for software to avoid just exactly such export restrictions and the source code is available.