Worlds of Ultima: The Savage Empire and Ultima: Worlds of Adventure 2: Martian Dreams are available now on GOG for free, courtesy of GOG and Electronic Arts.
Lord British presents two adventures in Ultima universe. Players of the Ultima series may recall that the black moonstone the Avatar found at the start of Ultima 6 can be used to teleport you anyplace and anytime. That is why ORIGIN Systems have, using the Ultima 6 engine, sent the gamers worldwide on two unexpected journeys in both space and time.
To download the game a (free) Gog account is required.