This type of use is not covered by the license, sorry.
I bought the tileset and love it but I had a similar kind of question as dreii.
For my game project, I'm building a campaign editor so players could create their own content, but the content could only be run through the game itself, not used to create a separate project that could be run on its own. The player would have to run my game, navigate the list of campaigns, and select one to run. The tiles would be compiled into my game (Monogame, so they would be xnb files) and if a player shared the campaign they created with another player, they would not distribute your tiles, their campaign data would just contain references telling my game which tiles to use when running it.
Would this usage be acceptable? Thank you for reading.
I admit it's a bit murky in this case! For the user-campaigns in your project, I wouldn't consider them derivative work, since it's all contained within your game. So this is fine!
If the users were able to create their own independent projects using your campaign editor that they could distribute (and their own users could play without using your project), that would cross the line. For that sort of purpose, you would need a sort of distribution license, since the scope is so different and could directly conflict with my own distribution of the assets.