Regarding Lovecraft inspired games, I'll just leave this here:
http://lovecraft.wikia.com/wiki/Copyright_status_of_works_by_H._P._Lovecraft
Chaosium, publishers of the Call of Cthulhu role-playing game, have a trademark on several Lovecraftian phrases and creations, including "The Call of Cthulhu", for use in game products. Another RPG publisher, TSR, Inc., original publisher of Advanced Dungeons & Dragons, included in one of that game's earlier supplements, Deities & Demigods (originally published in 1980 and later renamed to "Legends & Lore"), a section on the Cthulhu Mythos; TSR, Inc. later agreed to remove this section from subsequent editions because of Chaosium's intellectual property interests in the work.
Regardless of the legal disagreements surrounding Lovecraft's works, Lovecraft himself was extremely generous with his own works and actively encouraged others to borrow ideas from his stories, particularly with regard to his Cthulhu mythos. By "wide citation" he hoped to give his works an "air of verisimilitude", and actively encouraged other writers to reference his creations, such as the Necronomicon, Cthulhu and Yog-Sothoth. After his death, many writers have contributed stories and enriched the shared mythology of the Cthulhu Mythos, as well as making numerous references to his work.