so, uh, the GPL's text proposes that an interactive-mode program should display something like this when starting up:
<program> Copyright (C) <year> <name of author>
This program comes with ABSOLUTELY NO WARRANTY; for details type "show w".
This is free software, and you are welcome to redistribute it under certain conditions; type "show c" for details.
and i just realized that this is awfully similar to the way GDB's interface works. the notice is different, and the commands are show copying and show warranty instead, but you can see how the two are related.
if anything, this makes me think that the text used in the GPL might have been taken from an earlier version of GDB, back when show had fewer possible parameters and it was possible to unambiguously assign show c and show w to "show the program's license" and "show the warranty info"...