All original work I contribute to Wikipedia is public domain.
This means that although use of Wikipedia is restricted by the GFDL, any substantial section which I wrote can be used completely freely. There is no obligation to credit Wikipedia or myself as author, and there is no requirement that your use of it be under the GFDL or any other license which guarantees free distribution. The public domain is not a viral license.
Note that just because I started or rewrote an article doesn't mean it's my original work. You have to establish from the edit history that I created the section you want to freely use. For example, look at [1]. You might think from this diff that the entire red paragraph is in the public domain. But the checkin comment says "(Merge in information from Criminal Violence, Criminal Justice)", so you can't tell from this whether I wrote that paragraph or not.
Onebyone 20:31, 25 September 2006 (UTC)