1. Of the literally hundreds of maps on his site, there are only two which are actually based on Middle Earth.

2. 'Style' is not copyrightable. No one owes royalties to Picasso for Cubism.

3. Plagiarism is representing someone else's work as your own. The tag line of his site is literally "Tolkien Inspired Cartography". He's very clear that he's following Tolkien's style.

4. Tolkien borrowed from previous cartographers, his own style evolved considerably over time and what you probably think of as the iconic Tolkien map, was actually by Pauline Baynes.