Wikipedia allows you to reproduce its content.
If you want to use Wikipedia materials in your own books/articles/websites or other publications, you can do so -- but only in compliance with the GFDL. See here.
I am considering using some wikipedia content to pad out pages on my website. For example - just taking the first couple of paragraphs. The motivation for this is not for SEO , but to provide information to the website user.
My question is: by doing this will I hurt my own page SEO? I have googled around and mentions of Google Supplemental index keeps cropping up.