ianal. to the best of my knowledge the project is clean from a legal perspective. ofc, you don't have to be doing something wrong to become a target of copyright trolling.
(Not that if he made a high-performance interpreter it'd be a bad thing legally: the reason GNU's programming guidelines are so archaic is partially because everyone implementing GNU early-on had seen the UNIX source code yet they could get around getting sued by writing esoterically.)