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I have a somewhat embarrassing admission: I've been working in (or at least near) open source software for a little more than two years and, before All Things Open last month, I didn't really understood the subtleties around different types of open source licenses.

I wasn't a total IP ignoramous. I even took a graduate-level class in media law while I was in journalism school and we covered copyright in great detail. So, I understood that according to US law, everything was copyrighted upon creation (or more accurately, when fixed in a set medium). And I understood that there were open source licenses that essentially released works from copyright.

But (here's the admission) I thought "copyleft" was a specific license. I learned otherwise when Andrew Hall, a lawyer with Fenwick and West, LLP, who specializes in IP law, explained in his Open Source Licensing & Business Models talk that copyleft is not a specific license, but rather a term that describes all licenses that allow derivative works, but require derivates (if distributed) to use the same license as the original work.

Ahhhh! Now that makes more sense. He went on to explain that not all open source licenses are copyleft -- there are permissive licenses (like the BSD and MIT licenses), which mean that software released under that license can be used in programs that are distributed under any other type of license, including proprietary ones. The whole talk was similarly enlightening, and he covered copyright in great detail. Fortunately, Hall's talk was recorded:

To learn more about the concept of copyleft, visit, a new site the Software Freedom Conservancy and the Free Software Foundation announced earlier this month.

If you'd like to see what else happened at the event, the All Things Open YouTube channel now has video archives from many of the talks, including:

  • The Culture of Open Source panel:
  • Introduction to PaaS for Application Developers (by Steven Pousty)
  • OpenStack + OpenShift ^ xPaaS (by Burr Sutter):
  • Women in Open Source Keynote (by DeLisa Alexander):
  • Women in Open Source Panel (moderated by DeLisa Alexander, featuring Dr. Megan Squire, Elizabeth Joseph, Erica Stanley, Estelle Weyl, and Karen Sandler)
  • OSAS Open Standards Panel:

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