Author of djbdns and Qmail, among other things.
His home page is at http://cr.yp.to/djb.html.
He doesn't give his software a license, so it defaults to normal copyright (ie, only he is allowed to distribute). He makes an exception for unmodified source code, so most of his software is distributed as the original source code along with massive patches. This is enough to mean that his software doesn't meet the required definition of Free for inclusion in Debian, for example.
Read Rick Moen's rants pages for details and examples of problems with DJB's code.