As writing in WordPress theme page:
Contrary to popular belief, GPL doesn't say that everything must be zero-cost, just that when you receive the software or theme that it not restrict your freedoms in how you use it.
Basically i am talking about companies like themeforest that charging extra money for WordPress MultiSite:
I am not lawyer or something but i remember thesis gpl war in past:
Isn't it wrong against GPL? Dont we have rights to use proper licensed themes in multisite?