P.S. to: plungins and licensing

[Joern Rennecke]

To give it a bit more legal bite with respect to ruling out accidental
infringement, I suppose the passphrase could include a statement that
assures that the sending program is licensed under the GPL.

Another thing is that if it is considered possible that the passphrase
an be distributed as a separate entity and merely aggregated with the plugin,
it could be licensed under a more stringent license than the GPL which
is more effective at attaining the goal of requiring GPLed plugins.
The plugin interface could compute a cryptographic hash which the license
can then allow to be licensed under the GPL so it can be included into
cc1 binary.