[1] http://www.gnu.org/licenses/gpl.html
[2] http://archives.cnn.com/2000/TECH/computing/03/28/cyberpatrol.mirrors/
[3] Open Source: the Unauthorized White Papers, Donald K. Rosenberg, IDG Books,
2000. Quotes are from page 114, ``Effects of the GNU GPL''.
[4] In the "What License to Use?" section of
http://www.oreilly.com/catalog/opensources/book/brian.html
This whitepaper is a condensation of an original work available at
http://alumni.cse.ucsc.edu/~brucem/open_source_license.htm