CC-BY 4.0

1. Share — copy and redistribute the material in any medium or format for any purpose, even commercially.
2. Adapt — remix, transform, and build upon the material for any purpose, even commercially.
3. The licensor cannot revoke these freedoms as long as you follow the license terms.

With the above in mind, CC-BY 4.0 allows anyone to take these and repackage / resell them providing they follow the requirements of the licence.

Excellent textures!

However, Tsorthan Grove is correct: all licenses on OpenGameArt allow for resale. This is by necessity. Saying "you can't resell it" creates unintended legal entanglements that make the assets effectively unusable. Unfortunately, specifying "you can sell it within a game, just not by itself" doesn't resolve it.

The good news is, it is already pretty difficult for someone to resell them by themselves; The license, CC-BY 4.0, requires that a potential reseller must credit you and link to this page (or your home page). Anyone who might want to buy the assets from the reseller would see that it is available for free and not bother paying the reseller.

With that in mind, would you be willing to forego the "no reselling" restriction? Until then, I must mark it as having a licensing issue to prevent people from using it in a way you may not approve of.

EDIT: Fixed, thanks! :)