- CC-BY-SA is fantastic for collaborative prosaic content, or content that's intended to be read and interpreted by human beings.
- CC-BY-SA isn't a software license. It's not the best license for content that's intended to be read and interpreted mostly by machines.
- Software licenses aren't really as good as CC-BY-SA when it comes to prosaic content. The clear attribution requirements of CC-BY-SA help us stay ahead of bad actors, like SEO scrapers - but don't get in the way of people legitimately (and honestly) re-using our content. The goal for code was to be a bit more permissive, but there's no reason to be more permissive when it comes to prosaic content - we already have a great balance there.
- We don't think there's a 'universal' license that could serve us as well as two very specific licenses, one for prosaic content and one for code. As we burned through a ton of ideas, we kept landing on separation of concerns being the best path forward. We could have been wrong, but I'm just explaining how we arrived there.
Now, Tim rambles introspectively for a bit:
The biggest reason for going in this direction is that it makes our job as custodians of your contributions much easier if we transition into a more permissive code license. Any change can't weaken our stance in a never-ending war against SEO scrapers that started in late 2009.
How permissive all of you want the code license to be is something you're currently discussing. I'm just narrating our thinking and position at the time we reached it, with the MIT license in mind.
Put aside for a moment the complexities of trying to define code. Simplified, you end up with is content that is prosaic in nature - or meant to be read. You also have content that is non-prosaic, which can be read, but is mostly meant to be interpreted by machines. We want much tighter restrictions on what folks can do with prosaic content, and separating the concerns is the only way to achieve that. We don't need to make it any easier for people to just read stuff, essentially. That's easy enough.
CC-BY-SA is a fantastic license for prosaic content, and we definitely want to keep it. The attribution requirements help to ensure that 'mirror' sites don't outrank the original because the links back help search engines to identify them.
I'm not sure if all of you noticed, but we tossed in a proposed change to our terms of service at the same time that we added the proposed option for folks not to carry the MIT license (neither change is yet in effect). We put ourselves in a position where we can better enforce the terms of both licenses on your behalf (upon request of the copyright holder, or Stack Overflow, Inc.)
We're not the copyright holder - you are, you just give us a perpetual license to distribute your contributions. But, we're also the people folks look to for enforcement. I'm pretty sure we're going to want to close that gap in whatever scheme we ultimately end up with.
So let's say purely for the sake of discussion that the community broadly supports a 2 or 3 clause BSD-ish license. Just like CC-BY-SA isn't so ideal for software, BSD-ish licenses aren't so ideal for prose (though, it's generally okay for documentation). CC-BY-SA has everything we want on that side.
We should have been much more forward about this because we are doing some really good things to help ensure that we take good care of what you give us. The enormity of all the moving parts we were dealing with just .. well, never mind - we're talking about it now.