Proposal: Code commissions
From the Creative Commons FAQ:
Can I apply a Creative Commons license to software?
We do not recommend it. Creative Commons licenses should not be used for software. 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 at the Open Source Initiative. Unlike our licenses, which do not make mention of source or object code, these existing licenses were designed specifically for use with software. Furthermore, our licenses are not compatible with the GPL, the most frequently used free software license.
Note that the CC0 Public Domain Dedication is GPL-compatible and acceptable for software. For details, see the relevant CC0 FAQ entry.