D&D's always worked like this.
I mean, look at WOTC's claimed "intellectual property". The beholder, written by Terry Kuntz, published by Gary Gygax in Greyhawk without even a thank-you (corrected in the Monster Manual in 1977). The displacer beast, borrowed without consent from the coeurl in an A.E.Van Vogt story. The githyanki, githzerai, and slaadi, submitted by a teenage Charles Stross to White Dwarf. (His other works, such as "Zytra, Demon Lord of Mind Flayers" didn't quite catch on...) The whole apparatus of hobbits (sorry, "halflings"), wargs (sorry, "worgs"), ents (sorry, "treants"), balrogs (sorry, "balor") and so forth borrowed without consent from Tolkein. I mean, Gary Gygax even used Tolkein's misspellings ("dwarves", "dwarven".)
Don't be dumb. Protect your IP.