From Homestar Runner Wiki
On April 19, 2006, I sent an e-mail to the Wikimedia Foundation official e-mail address inquiring whether it was considered fair use to use the logo I created. On May 19, 2006, they finally replied. I have quoted their exact reply here for future reference. Well...it wasn't actually styled as a Strong Bad e-mail when I received it, but I thought it'd be more appropriate to preserve it in that form here.
subject: Re: [Ticket#2006042010002674] Question on Wikimedia-held Copyright
Hi Gordon. I'm the lawyer for the Wikimedia Foundation.
In response to your request, you are granted permission to use the puzzle globe logo you reference, provided you do the following: (1) include the statement "The puzzle globe logo is copyrighted by the Wikimedia Foundation, Inc. Used with permission." and (2) "Homestar Runner" is not associated with the. This must accompany *any* use of the logo. If you intend to put it up as the main logo, this statement should be included in the footer of the site.
Your administrator should be able to do this.
Thank you for your interest in Wikipedia.