Dang, I was going to try to refute you by saying no license meant no restrictions, but nope! Creators of software (and any written work apparently [1]) are automatically granted copyright for their work (this makes sense) so without a license, copying it would be a violation of copyright. That's wild, but seems reasonable.

Posting it to Github isn't implicit permission, but it would probably be a factor if the author did try to sue people for using his or her copyrighted work without license/permission.

[1] http://en.wikipedia.org/wiki/Open-source_software#Open_softw...