Yes, right. Thats the reason, why blender is "free".

But however, you can define what you wanna get for your product.
Shure, for my 2.5D Spaceshooter i'll never get 100thousand $,
but maybe 100 $ (100 people donate 1$/person). and if i finish my 3d spaceshooter i could sell it as an finished game, than as an open-source with all files and data, and than a "book" or a manual about it (title "How to use the source", or "how to create an add-on"). So i could create a line of sell-able products around one "main-product".

(i hope you can understand what i am talking about,.... sorry for my handy-english )