casuarius is a Cython wrapper for the Cassowary incremental constraint solver.
The solver source code is derived from the 0.6 release. It has been modified by Svilen Dobrev to remove memory leaks. His work can be found separately as SWIG bindings:
His modifications are available under the BSD license, while Casuarius as a whole follows the license of Cassowary itself, LGPL v2.1 or (at your option) a later version of the LGPL. See the files LICENSE and COPYING.LGPL for details.
Please be sure to have Cython 0.15.1 or above in order to compile this extension module. It has been tested on OS X (using llvm-gcc 4.2) and Windows (using mingw). Other Windows C++ compilers may or may not work.