Antimony is a text-based model definition language originally based on Jarnac, and extended to be fully modular. Antimony models can be converted to and from SBML, flattening the modularity in the process. See also: Features of the Antimony language
The sourceforge default Antimony project page can be perused for bug reports, source code, and links to earlier versions of Antimony.
libAntimony is distributed under the BSD License. The Windows binary includes a libSBML dll, which is released under the LGPL. libSBML, in turn, relies on expat, released under the MIT license, the gzip dll, released under the GPL, and a bzip dll, released under the BSD license. DLLs from the CellML API are also included, released under a triple GPL, LGPL, and MPL license. In addition, QTAntimony comes with QT dll's, which are released under the LGPL