I am working on a battle system that loosely based on the d20 system that has a Open Game License. I am only using the mechanics of the system, no artwork or trademark names. Will this hinder a game from being published?
No problem with that in Europe however, no idea in Usa. In theory would be inside of fair use you are no blunty copy copyrighted material from it and the system ifself is used by almost all rpg dice system. Just put it in credits system lighty based in d20 open source material
US copyright law is…interesting. Hasbro likes to exercise their rights - alot, but I doubt OGL allows them to do that. Provided you aren’t lifting interpretations of a game system (so copying one of their books), and are just using the ideas behind the system, and no IP. You should be fine. OGL is tricky though, wikipedia says it’s share-alike which would suggest you need to publish the game under OGL aswell…
Need a lawyer. xD
EDIT: As far as I understand it, Game Systems are not copyrightable. (Source: http://www.earth1066.com/D20FAQ.htm#D.05_) [Accessed 2016/06/08]
From what I know, games can be copyrighted, but game mechanics can’t. And there, is my limited knowledge.