Obfuscation and Copyleft Licenses
There has been debate on whether it is illegal to skirt copyleft software licenses by releasing source code in obfuscated form, such as in cases in which the author is less willing to make the source code available. The general consensus was that while unethical, it was not considered a violation. The issue was clarified for the GNU General Public License when it was altered to require that the "preferred" version of the source code be made available.
Read more about this topic: Obfuscation (software)