As far as I know, Sierra has never released source code for any of their games. Some people have reverse-engineered some of the SCI games to effectively get the source, but Quest for Glory 5 was written in C++. The code is much more complex than that of an SCI game.
The original QG5 demo featured limited multiplayer play. If I recall correctly, you could see other players and talk to them, but not really interact otherwise. QG5 was designed to be both a solitaire and a multiplayer game, but we greatly underestimated the challenge of creating and testing an MMORPG. After QG5 was released, we looked at making a multiplayer version of it and concluded that we couldn’t get it done under any reasonable budget.
Lately Lori and I have been spending almost every non-working hour playing World of Warcraft. If we had created QG Online and it had come out half as well as WoW, we would have been very proud of our accomplishment. WoW has a lot of software bugs, but the game balance, quest, and guild mechanics are wonderful. (We play Horde characters on Silver Hand and Alliance on Earthen Ring, may eventually get back to playing our Night Elves on Shadow Council.)
– Corey Cole