What license to choose for a model which we will freely distribute?
The site http://choosealicense.com/ will probably be helpful to you. The front page of the site offers a simple choice in fairly plain language:


I want it simple and permissive. The MIT License is a permissive license that is short and to the point. It lets people do anything they want with your code as long as they provide attribution back to you and don’t hold you liable. jQuery and Rails use the MIT License.

I’m concerned about patents. The Apache License is a permissive license similar to the MIT License, but also provides an express grant of patent rights from contributors to users. Apache, SVN, and NuGet use the Apache License.

I care about sharing improvements. The GPL (V2 or V3) is a copyleft license that requires anyone who distributes your code or a derivative work to make the source available under the same terms. V3 is similar to V2, but further restricts use in hardware that forbids software alterations. Linux, Git, and WordPress use the GPL.



The site also has a more in-depth page giving more choices, and more detail about the differences between licenses.
I would strongly advise that you don't use a Creative Commons license for your code. Creative Commons themselves caution against this:

We recommend against using Creative Commons licenses for software. Instead, we strongly encourage you to use one of the very good software licenses which are already available. We recommend considering licenses made available by the Free Software Foundation or listed as “open source” by the Open Source Initiative.

More detail in their FAQ.
Personally I use the GPL (version 3) for most of the code I release. For very small programs -- roughly speaking, anything shorter than the license text of the GPL itself -- I tend to use the MIT license. This is partly because I'm less concerned about the fate of such small code snippets, and partly because it feels a little silly to have more license than code in a release.
As a side note -- although you haven't mentioned this possibility -- please resist any temptation to invent a new license, unless you have a really compelling reason. License proliferation is a big problem, and your code will be less useful if people have to pay a lawyer to determine whether your license is legally compatible with some other software they're trying to use in conjunction with yours. In general, I would suggest picking one of the &quot;big three&quot; mentioned above unless you have specific reasons against this.
Edit: I just saw your comment about the appropriateness of using a GNU license for Matlab code. There is no problem here: there is no concept of &quot;contamination&quot; between the license of your code and the license of the language it's written in. In fact, it would be hard to implement such a restriction, because languages as such don't have licenses: only their implementations do. Many programming languages have both closed-source and open-source implementations -- this includes Matlab, although Octave, the GPL implementation of the language, is not 100% compatible with the original version. However, for Matlab specifically, you might want to consider the BSD license, because it's the only one permitted on MATLAB central. (If you never intend to share your code on MATLAB central, this is less of a problem.)