Hi Guys, I'm in the process of making my own game engine which has some unique features. I'd like to release it under an Open Source license to maximise the amount of exposure it gets (and hopefully get some community projects on it) but I don't want commercial projects taking my hard work for free so I'd like some kind of commercially unfriendly license. I can then offer a friendlier license for a fee. The typical solution would be the GPL, as is used by Qt for it's open source license. This works great if you are producing a library because companies generally want to keep their source to themselves and not open it up - hence they can't use your library. But what do you do if your producing an application? If I use the GPL might a company decide to use it (releasing their source of course), safe in the knowledge that no-one can use their game without the art, sounds, scripts, etc which are needed to complete their game? Basically, it seems to me that a companies art, sound, etc are more valuable to it than it's source code. Even if the source code is valuable, they gain nothing from paying for a commercial license for it as the GPL version is still in the open (unless, of course, they need to significantly modify the code). Are there any Open Source licenses which would require the company to release all it media (maybe under the creative commons license) if they use my engine? I'm sure this would encourage companies to pay the fee. Thanks in advance for any help!

That's extremely useful information, I'll check it out more thoroughly.

Thanks a lot!

Quote:In other words, if they're distributing a game which consists of game engine + content, the content also has to be released under GPL. Which isn't the best license to use for media, but it'll do.

I think he was asking "what if I release an application open-source and a game company takes my source but adds their own content and sells it?" I can't think of a license that prevents non-open-source content from being sold with your open-source engine. That would be like attaching a license to a music player that reads "you may not distribute closed-source music with this player."

However you're more than welcome to write your own license that includes that kind of clause. Most open-source licenses are attempts to protect the source code from theft or closure, not to kill all commercial viability. In my opinion, that will only limits the kind of exposure you can get for your project.

EDIT: What you're suggesting (selling your more friendly license for a fee) will almost undoubtedly require writing your own license, as it's so specific it can't fit into many projects. Check out fmod as one project that is free for non-commercial use but requires payment for commercial use: this should suit your needs fine. You are then more than welcome to sue anyone who uses your code in a commercial project without paying royalties.

Hmmm... it's clearly a complex situation. Actually I guess it's similar to the Quake series of engines, which have now been released under the GPL. Does anyone know of any commercial games which have been based off the open sourced Quake engines? What did these companies do with thier media assets?

[edit:] the Problem with creating my own license is that I don't believe people would understand it. The Open Source people know the common licenses and would most likely reject something that wasn't at least OSI approved. Plus it's a big task, the GPL is complicated because it has to be.