10$ is for the whole bundle ( commercial license and access to paid content for all 4 asset packs )
You can buy them individually on the end of the page of each asset.
Viewing post in Pixelarium - Grasslands 16x16 Tileset comments
Yes, you can't redistribute the asset because that would destroy my product, as you could get it for free somewhere else.
But it's possible to discuss a standalone version of the asset for educational use, my asset has been used before for the same reason (check None's Class RPG series)
Send me a message at Discord: lukethepolice if you're interested to discuss the idea.