Creative Commons' FAQ addresses this

    Unlike software-specific licenses, CC licenses do 
    not contain specific terms about the distribution 
    of source code, which is often important to ensuring 
    the free reuse and modifiability of software. 
    Many software licenses also address patent rights, 
    which are important to software but may not be 
    applicable to other copyrightable works. Additionally,
    our licenses are currently not compatible with the 
    major software licenses, so it would be difficult to 
    integrate CC-licensed work with other free software. 
    Existing software licenses were designed specifically
    for use with software and offer a similar set of 
    rights to the Creative Commons licenses.