"Attorney David Loundy's clients never meant for their
database to be free software or for its code to be open source. But
when a database contractor used snippets of code copyrighted by the
GNU General Public License (GPL), the clients were shocked to find
they couldn't sell their own software as a proprietary work.
Because of the way the GPL is written, if you, your staff, or
your contractors use code that falls under this copyright license,
the end product must also use the GPL. It's a lesson that many more
development managers are likely to learn the hard way, especially
if they draw heavily from GNU or Linux communities, which rely on
this license. Here's a look at the history and purpose of this
popular license and the ways it can affect you."