I thought it was pretty clear in the description. These tiles are for non-commercial use. That means: not private, but you can't use them for anything that's trying to make money. So whether you can use them depends on your intentions.
The threshold for deleting them would usually end up deleting the contents of other tiles. In the end I created a diff layer to identify where the tile contents were vs the checker background, and used that to generate a non-destructive mask to remove the checkers resulting in an image with an alpha layer.
thank you so much for all of your creations. as someone whos making maps in tiled for my projects, these assets provide a great way to practice object and tile placement. thank you for what you do :)