Did you even read the article? He says "one fork is being sold with a comercial [sic] license". Commercial licence != GPL.
http://www.gnu.org/licenses/gpl-faq.html#DoesTheGPLAllowMone... Does the GPL allow me to sell copies of the program for money? (#DoesTheGPLAllowMoney) Yes, the GPL allows everyone to do this. The right to sell copies is part of the definition of free software. Except in one special situation, there is no limit on what price you can charge. (The one exception is the required written offer to provide source code that must accompany binary-only release.)
Until there is more evidence this is just a developer who misunderstands what the license entitles others to do with his work.