Sonetto is a New BSD License licensed project, and all other libraries it uses are GNU LGPL'ed. Both licenses allow works protected by them to be used in commercial software, so commercial software does is allowed, although LGPL imposes some nasty restrictions in the way this happens. Basically, LGPL code can only be linked to commercial code by dynamic linking methods. Instead of dynamically link against a thousand libraries, however, one can do so once with Sonetto, which itself is statically linked to the libraries it uses.