What does "Free" mean in the context of licenses? Looking at a few of those it appears that some don't actually specify, which is dangerous:

"Because I did not explicitly indicate a license, I declared an implicit copyright without explaining how others could use my code. Since the code is unlicensed, I could theoretically assert copyright at any time and demand that people stop using my code."

http://www.codinghorror.com/blog/2007/04/pick-a-license-any-...