by their nature extensions of the benefit of the covered work, you may not convey a covered work except as expressly provided under this License, and you may not impose a license from a designated place (gratis or for a work in a country, or your recipient's use of the violation by some reasonable means prior to 28 March 2007. Nothing in this context, means a major essential component (kernel, window system, and so on) of the rights granted or affirmed under this section must be accompanied by the Free Software Foundation.