I have used Redsn0w for jailbreak my iPhone one year before but recently i never heard about this application update. Why they are not updated for iOS 6 and 7.
Because it was replaced by the evasi0n tool. Has to do with the way the jailbreak is done. Redsn0w was more suited for the older apple devices. Why update an old tool that does not add anything anymore but takes lots of time and effort from the Devs.
Same reason we don't use windows 98 any more. Newer and better software is out. You can only update old stuff so much till there's time to replace it with something else.