In a lot of ways, that’s all you need to know.
This week, I’ve been informed by folks in the Twine community of a couple developments: that Twine has been placed on Steam Greenlight by someone who is running a crowdfunding campaign for same, and that someone had set up a page on itch.io to sell binaries of Twine for $5. (itch.io has since taken this page down.)
Right upfront, I’ll state that nobody has previously communicated with me about any of these things, so you can consider them unauthorized by me — which I italicize to stress that I’m speaking for myself only.
But, besides that– is it legal to put Twine into an app store regardless of my own personal wishes, let alone charge money for it? I’m not a lawyer, obviously. But I believe the answer is yes, if that distribution complies with the GNU Public License v3 (or GPLv3), which is the license I chose for Twine 2. (I used GPLv2 for Twine 1.x.) In particular, sections 4, 5, and 6 describe the requirements for distribution in what I think is pretty plain language.
One nuance of the GPLv3 that you may not be aware of is that it allows for a fee to be charged for distributing the software — but there are two major requirements. First, the distribution must include source code or otherwise make it available to end users. Secondly, it requires that customers be also allowed to distribute the software themselves, for free or for cost. So, there’s no point in charging for a GPL-licensed application, since anyone who ponies up whatever cash is allowed to then give it away to the entire world for free.
Before I move on, I’ll also point out that works you create with Twine are not governed by the GPL. The story formats that your work is bound to — Harlowe, Sugarcube, and Snowman — have more permissive licenses that largely only require you to credit them appropriately.
That said, there’s something here that I especially don’t want to discourage, which is people asking for donations to expand Twine’s capabilities. It would be hypocritical to do otherwise, considering I’ve set up a Patreon to do exactly that. Again, the GPL places limitations on this. If you create a derivative version of Twine, it must also be released under the GPL — and ideally, you would contribute those changes to the main source repository. You are not permitted to take Twine, change it, and then offer it under a different license (in particular, a proprietary one).
Obviously, you should use the same judgment that is appropriate when evaluating any crowdfunding campaign. I don’t know the person running the crowdfunding campaign nor have I spoken with them, as I mentioned above, so I can’t really speak to its viability. You’ll have to draw your own conclusions.
I’ll close with why I haven’t put Twine in app stores like Steam, itch, the Mac App Store, and so on thus far. Right now, I have my hands full supporting mobile browsers and all three major desktop OSes — producing separate versions for the various stores, let alone supporting them, is too much for me to consider right now. Though that may change in the future– who knows?
Speaking of, I’m looking for someone to assist with managing the Linux version of Twine. There were a number of Linux-specific bugs that made it into 2.0.10 because we didn’t test on that platform as much as we did Windows and OS X. If you’re interested, please drop me a line.
Edited on 20 December 2015 to clarify that changes to Twine must remain under the GPL, as specified by the terms of the GPLv3.