I once knew an old grognard who loathed both Rona Jaffe and the game Rogue. Back in '79 he wrote a rules-lite fantasy game for solo play or BBS play called Mazes & Monsters. He hates how Jaffe (and Tom Hanks) is credited with the name, and Rogue with the interface, both of which he claims are rightfully his.
The Midian DFRPG gets mixed up with roleplaying games for Second Life, Nightbreed, and the Dresden Files.
Palladium Books at one time published a game called NightSpawn. However, this was rather close in name, and and somewhat similar in theme to Todd McFarlane's Spawn comic line. Thus editions after the first were renamed to Nightbane due to the apparent intervention of lawyers.
I actually have a book with the "NightSpawn" name still intact that I found at used book store, and so far as I know, that the only difference between the first and second printings.
I understand the need to protect one's trademark, but I still feel that that was just an example of McFarlane being a jerk. I half expected him to go after other targets next, leading down a destructive path that eventually found him trying to sue salmon for swimming upstream to spawn.
I think the line is pretty clear. If someone tries to rip off your idea to make money for themselves, without even crediting you then it's crossed. However is that what was happening here? I don't think so.
You can be inspired by something without plagerism