Cool tree.

Unfortunately, the stipulations about not selling it conflict with the license you've selected. CC-BY (and all other licenses on OGA) allows people to try to sell assets. I doubt they'd be very successful considering they are also required to link back here where their potential customers could see that it is free, but they are still allowed to try. 

This isn't because we want other people to profit off of your hard work. It's because it creates legal problems for developers trying to use it in their game. Even if they are only selling it as part of the game, the law gets murky with what counts as "sell as an item by itself" 

Would you be willing to remove the text about not being allowed to sell it? Until then I have to mark this as having a licensing issue so others don't try to download and resell it like the license allows. Let me know if you have any questions. :)

EDIT: thanks! :)