[DeveloperX]

Okay, I'm making a c++ game engine / library that wraps SDL and Allegro behind a nice easy to use common interface.

I am thinking of releasing it as open source, but its not clear how to go about it, nor what legal rights I really maintain.

I don't want to spend all this time on this and then have someone rip my project from me and call it theirs, obviously.
And I don't want someone getting rich off of my hard work.

So, my question is, would you guys explain how it all works (don't just give me links to gnu's website, cause its confusing as hell to me)
I've read the GNU GPL license several times, but I cannot make sense of it........I hate reading legal jargon......


If I release my engine/library under the GNU GPL am I protected from people ripping me off, and or selling my code to the highest bidder, etc..?

I've already implemented a large portion of the library, and I'm going to make a few sample games to ship with it, like a ball+paddle (breakout/pong/etc), a side scrolling space shooter (rtype/gradius/etc), and a very small rpg to demonstrate the abilities of my engine, as well as gain some experience writing the games. ;)

Any help/advice/criticism/etc is welcome and appreciated.
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Principal Software Architect
Rambling Indie Games, LLC

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[Rainer Deyke]

In practical terms, you have nothing to worry about. Nobody will sell your code, because nobody will be willing to pay for it. Probably nobody is going to use it either. There are so many open source game engines around that nobody is going to care about another one. If you want people to use your engine, you're best of releasing it under a very liberal license without worrying about the possibility of somebody making money off it. I like the Boost license, which is very clear and readable. If you don't want people to use it, don't release it.

To answer your specific question about the GPL: the terms of the GPL will prevent many people from using your engine, but there's nothing in the GPL that prevents people from reselling your engine.

If you specifically want to prevent people from reselling your engine, you'll need a license that specifically prohibits this. Either look for one, or write your own license.

[Bjorn]

Well sure the GPL doesn't prevent people from reselling your engine, but they will have to do so under the terms of the GPL, which is to give anybody they manage to sell it to also the same freedom to modify and redistribute under these terms. Anyway your other point is of course completely valid. Unless the engine features anything beyond the state of the art, it's not commercially interesting.

Making the library GPL doesn't prevent any people from using it (GPL gives freedom, remember), it only requires them to also license their game under the GPL (want freedom? give it, too). Of course there's nothing preventing them from dual-licensing the actual game under a GPL-compatible license like the Boost Software License.

As for the state of the art, there's already higher level APIs around like ClanLib (wraps SDL and OpenGL) or OpenLayer (wraps Allegro and OpenGL). There's also libraries like Guichan, which define a common graphics interface through which any library can be supported.

I did the same in the engine used in On a dark Sunday, which supports Allegro, SDL and OpenGL this way. However the features of these libraries differ, and On a dark Sunday depends on some features that only the OpenGL backend offers. I don't really see the benefit of supporting the same set of features on different graphics libraries, other than supporting both software and hardware rendering.

[DeveloperX]

bleh...okay, I've read all the text I could find about free software licenses (according to gnu.org & fsf's site..forgot url).....and it has completely turned me off of releasing my engine.

So, yeah, forget this thread.
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Principal Software Architect
Rambling Indie Games, LLC

See my professional portfolio

[Nodtveidt]

If you have an engine worthy of licensing, don't do it under the GPL, sell it under a commercial license with strict usage terms, including "you can't sell the engine code" (translated from legalese). The GPL certainly will prevent certain people from using it, as license clashes are very common with GPL-based libraries, and unless EVERYTHING a developer uses is GPL licensed, then they'll be breaking the GPL by using anything with an alternate license...unless those other things carry the zlib or BSD licenses, which, strangely, seem to be compatible with the GPL. But realistically, unless your engine is the "killer app" that developers have been dreaming about for years, you're probably not going to be able to sell it anyways, but at the same time, the chances of someone else selling it are monumentally slim.
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If you play a Microsoft CD backwards you can hear demonic voices. The scary part is that if you play it forwards it installs Windows. - wallace

[RedSlash]