One of the most intriguing possibilities of open source games is the ability to create interest in a game that has already come and gone as a commercial release. Myst Online: Uru Live was intended to be the multiplayer piece of 2003's Uru: Ages Beyond Myst, but its complicated development process led to a splitting of single player and multiplayer into two pieces, with the latter not being released until 2007.
While there was some curiosity about seeing what Cyan Worlds had done with the idea of multiplayer Myst, the game struggled to attract subscribers and was canceled after its first year. Disappointed with the turn of events, Cyan decided to release Myst Online: Uru Live as an open source game in 2010 hoping fans would be able to give the game a new life.
"I think everyone at Cyan that has worked on Myst Online as well as many fans feel like the full potential has never been realized," Mark DeForest, chief technical officer at Cyan Worlds, told me.
"It was mostly from those unfulfilled feelings that we reopened the MystOnline servers for free and open sourced. And we have seen some pretty fantastic stuff done by fans without the source and we wanted to see what they could do with the real stuff."
The first obstacle in the cast of Myst Online was untangling the rights to the game to make sure Cyan wouldn't be in breach of any of its previous contracts with publishers.
"It took many discussion to make sure that we were protecting all the different interests, and yet giving enough freedom to the fans to innovate," DeForest said. "Once the license was determined it set the tone and things just started falling into place."
Surprisingly, Myst Online had such fervent fans that many had already started making progress in reverse engineering large parts of the system before the source was actually released. "With open source games the roles are almost reversed, The community has a lot more of the control of the development and the developer has more of an advisory role, hoping we can point them in a general direction," DeForest said.
"And these fans spend an unbelievable amount of time on this. Sometimes I feel guilty about that. On one late Friday night when I was conversing with one of the fan developers, I suggested that we pick this up on Monday thinking he wanted to spend some time with his family. And he replied 'Oh, right. I forgot. You take your weekends seriously.'"
Derek Yu's well-regarded Spelunky, a procedurally generated cave exploration game, recently went open source as well. Spelunky was published independently by Yu so there were no complicated licensing arrangements to deal with. Likewise, the game sold well and received largely positive commentary from critics.
"I had two main reasons [for releasing the source code]," Yu told me. "My own understanding has benefited so much from looking at other people's code and I wanted to give beginners the same chance to learn from my work on Spelunky, without having to use a decompiler. Also, I think modding is a great way to entertain yourself with a game, and it has the potential to extend the game's life and bring it to new players."
Spelunky is an especially curious game to have gone open source because its foundation in procedurally generated environments and enemies meant the game already had a tremendous amount of built-in variation.
"The original touched on something that really resonated with players, but I think there's a lot more that can be done with the idea," Yu said. "There's a mod out there that lets you play as one of the enemies in the game and it changes the mechanics up quite a bit. I thought it was pretty cool. But to be honest, I don't keep a close eye on what people are making with the source -- I'm too busy trying to refine the concept myself, for the XBLA version of Spelunky."
Amazing things can still happen when you turn a mature piece of software over to the collaborative masses. Yu mentioned The Ur-Quan Masters, an entire game built from the Star Control II source code as an example. That fan-built game is now the basis for a follow-up game meant to serve as a "true" sequel to Star Control II since many fans disowned Star Control 3.