One licence you might like to consider is the Creative Commons Attribution-NonCommercial-ShareAlike 2.0 License.
This means that you are free:
Under the following conditions:
The formal legal conditions are described on the Creative Common Web site.
You might also like to have the Digital Code added to your IWMW 2007 page. If so please contact a member of the IWMW 2007 team.
It should be noted that presentations may contain screen images owned by others. Where possible citatations for these images will be provided (in the form of hypertext links to the source Web site).