Freebloks 3D for Android is free software, it’s open source, completely free of charge and you can modify it to any extent. Free software however does not mean it has no value. That’s why Freebloks comes with the feature of in-app donations to support the developers.
You can choose how much Freebloks is worth to you, you can donate any amount you like or you can purchase the new published version called Freebloks VIP, that is identical to the free version but paid to show the support to the developers. The only visual difference is the coin in the app icon indicating your support.
Please don’t take free software for granted.