Jeff Perren wrote the Chainmail rules for medieval wargaming together with E. Gary Gyax in 1972.
Jeff Perren still had the rights to Chainmailand 50% royalties until 2006.
Realizing the thing was not Trademarked he would have difficulty claiming infringement on his game title "Chainmail".
So Jeff, in need of money, settled with Hasbro for $500. (Thanks to Pauls Stormberg for this information.