I am developing a game whose code is open source. However, I want the game's content such as models and artwork to be under a proprietary license if they are my own work; i.e. the license wouldn't apply to sounds I got off sounddogs.com. I don't want to prevent people from studying the content, like seeing how a model was put together. This is specially relevant since I'll probably store things like my models' .BLEND files in my project repository. I just want to prevent the use of my content in someone else's finished product. My major motivation is to create a "brand" for my project. If people see a screenshot that has one of my models in it, they should be able to tell or figure out that it is my own game. My question is what would be the best way to create such a license? How detailed would I have to make it? How should I set it up so people can tell which files in my project the license applies to? Are there any existing licenses that already fit my needs?

The Creative Commons Attribution-Noncommercial-No Derivative (CC-BY-NC-ND) sounds like the license you're after. Not only is it already written for you, both in simple summary and full legalese forms, but it's also very widely known.

The NC and ND clauses are quite restrictive. Nobody can use your models in their own game, even if it's freeware, except perhaps for placeholder art during development (and even then they wouldn't be able to distribute the game until the models are replaced). It's debatable whether or not they could even distribute screenshots of your models in their game, since that may count as "building upon" your work, which the ND clause specifically disallows. Nobody can sell your model under any circumstances (in a game, in a collection of models, etc.), thanks to the NC clause.

Pretty much the only thing people can do is include your model, as-is, in a free model collection or free Blender tutorial or something, provided they attribute the work to you in a manner you specify. You can specify that anyone who distributes the models has to put your name, date, the game the model is from, and a URL to your website and/or your game's website.

Thank you for the suggestion. I thought the No Derivative clause only applied to people using modified versions of my assets as opposed to using the original assets in their projects, so I wasn't considering it. Thanks for clearing that up.

Does the Noncommercial clause apply to my own use of the assets, in case I want to use them in my own commercial project?

As an aside, I'm specifically using Google Code for my project hosting. They only have CC-BY and CC-BY-SA listed in their built-in interface, so I'll have to put my content license in separately.

Quote: Original post by The Blarg
Does the Noncommercial clause apply to my own use of the assets, in case I want to use them in my own commercial project?

Assuming that the assets you are talking about where wholly created by you then you are free to do whatever you want with them. A license is just there to tell everyone else on what terms you are allowing them to make use of your assets. Obviously if you got the assets from someone/somewhere else then their license terms would apply.