A few more thoughts, in the same vein as P-kitty's:
Belen, by the reasoning you've used, D&D itself is a collection of plagiarized ideas. It owes its magic system to Jack Vance, its treatment of Elves and Dwarves to Tolkein, many of its clerical spells to Biblical sources, etc.
However, there's nothing wrong with taking an idea and using it, as long as you give credit where credit is due. EGG did this with his appendix of reading material in the back of the first DMG.
Belen, by the reasoning you've used, D&D itself is a collection of plagiarized ideas. It owes its magic system to Jack Vance, its treatment of Elves and Dwarves to Tolkein, many of its clerical spells to Biblical sources, etc.
However, there's nothing wrong with taking an idea and using it, as long as you give credit where credit is due. EGG did this with his appendix of reading material in the back of the first DMG.