You're probably not going to have the FBI knocking on the door if that's what you're worried about (unless you do something silly like try to profit off them in any way). However, most of the games are still protected by copyright, regardless of their availability. Even titles by defunct companies (Exidy, for example) had their rights transferred to other parties (Mean Hampster Software in Exidy's catalog's case).
I don't think it's taboo to discuss the legalities of it. The only taboo is giving links to where to find them.