Google Knol is live. It launches with CC BY default.
Mike Linksvayer say, s prior to its launch Knol was often speculatively compared to Wikipedia, it should be noted that the default Knol license (CC BY) could permit using Knol content in Wikipedia (with attribution of course), but knols under more restrictive options could not be incorporated into Wikipedia. On the other hand Wikipedia content could not be incorporated into knols (except in the case of fair use of course), even in the case Wikipedia migrates to CC BY-SAhttp://creativecommons.org/weblog/entry/8213— Knol doesn't offer a copyleft license.
see http://creativecommons.org/weblog/entry/8506 http://blogoscoped.com/archive/2008-07-23-n20.html