For every brilliant fan-made project that borrows ideas and/or traits from popular licensed games, there are as many cease and desist copyright orders from big budget publishers that follow. This year alone has seen Nintendo step in on that really good Metroid II remake and No Mario's Sky, while Samsung wasn't exactly happy with the modders who mocked its ill-fated Note 7 handset.
DoomRL—the free fan-made roguelike Doom spin-off that was launched in 2002—has now fallen foul of ZeniMax's legal remit it seems, with the id Software owner issuing a legal letter to creator Kornel Kisielewicz. "So... Zenimax have just written to me demanding I take down the DoomRL site," Kisielewicz said last night via Twitter, alongside a copy of ZeniMax's letter.
As you can see, ZeniMax writes: "This unauthorised use of ZeniMax's intellectual property falsely suggests ZeniMax's sponsorship or endorsement of your website. This practice infringes on ZeniMax's exclusive intellectual property rights." The publisher then suggests its trademark be removed from meta tags, keywords and media.
While no one expects big budget publishers to advocate for projects, big or small, without receiving something in return nowadays, the context of this case makes it more peculiar than most. For one, DoomRL has existed for almost 15 years without issue and has always made clear its influence—I also don't imagine anyone would opt for a free fan-made ASCII-inspired roguelike over the real thing. ZeniMax has also publicly vouched for Brutal Doom—another fan-made project—however it's worth noting this is a mod for something they actually own.
Perhaps the tipping point here is Kornel Kisielewicz's involvement with Jupiter Hell—a "turn-based sci-fi roguelike" inspired by DoomRL and Doom itself that's in the middle of a live Kickstarter campaign. It bills itself as an "RPG with modern 3D graphics, by the creator of D**m, the Roguelike"—the stars, I believe, having been added following ZeniMax's approach.
Assuming it's seen through to completion, Kisielewicz serves to profit from Jupiter Hell which may be why ZeniMax has now chosen to intervene.