"The Gentoo/FreeBSD project, which combines the FreeBSD kernel
with Gentoo Linux design principles, is in a fix. Its lead
developer, Diego 'Flameeyes' Pettenò, discovered licensing
issues while working on the libkvm library and the
start-stop-daemon--and Pettenò says that the problem might
not be limited to his project, but could trap other BSD-derived
projects as well.
"'The licensing trouble began,' says Pettenò, 'when I
looked up the license under which libkvm was released, as I was
going to link into a GPLv2 software (portage-utils, a
Gentoo-specific utilities package), and I found it using the
four-clause BSD license (the original one, basically)...'"