flippant answer—tptacek doesn't "copyright" anything. in territories that recognize the Berne convetion of 1989, everything created that meats the standards for copyright is protected by copyright. you can't "copyright" something—something either is, or isn't protected by copyright. IANAL, but as tptacek's comments are tangible forms of creative works, they are trivially protected by copyright

less flippant answer—because he's probably had problems with people stealing his answers and posting them on other forums or similar issues.