From Meta, a Wikimedia project coordination wiki
Sj's form letter:
Wikimedia is migrating its license from GFDL to Creative Commons BY-SA 3.0. The latest version of the GFDL allows this, but only until August 1 of 2009. Have you considered making the same change? Wikimedia's migration means that partner sites licensed under the GFDL will no longer be compatible with Wikipedia content (you will not be able to import Wikipedia content, and Wikipedia will not be able to import yours). I am writing to major GFDL wikis such as yours to be sure you are informed about this change. Please let us know your plans. You can follow our outreach efforts here: http://meta.wikimedia.org/wiki/Licensing_update/Outreach
Kaldari's form letter:
Hello [Contact Person], I'm contacting you as a representative of Wikipedia to let you know about an important change in our licensing policy. As you may have heard, Wikipedia and other Wikimedia projects have voted to switch licenses to Creative Commons-Attribution-Sharealike 3.0 from the GFDL. This is possible because the latest version of the GFDL (version 1.3) has a provision to allow wiki projects to switch to Creative Commons. However, according to the terms of the GFDL 1.3, switching licenses is only possible if done before August 1, 2009. Because Wikipedia is changing licenses, it will no longer be possible to move content to and from Wikipedia (without violating the licenses) unless [name of Wiki Project] also changes over to CC-by-sa. Please visit http://meta.wikimedia.org/wiki/Licensing_update/Outreach for more information or email me if you have any questions. Thanks for your time.