Can I Use Wikipedia Data In my Computer Program?

Wikipedia's textual content is copyrighted, but you can reuse it with a license.

From the site, also linked below:

Most text in Wikipedia, excluding quotations, has been released under the Creative Commons Attribution-Sharealike 3.0 Unported License (CC-BY-SA) and the GNU Free Documentation License (GFDL) (unversioned, with no invariant sections, front-cover texts, or back-cover texts) and can therefore be reused only if you release any derived work under the Creative Commons Attribution/Share-Alike License or the GFDL. This requires that, among other things, you attribute the authors and allow others to freely copy your work. (See Wikipedia:Text of Creative Commons Attribution-ShareAlike 3.0 Unported License and Wikipedia:Text of the GNU Free Documentation License for full details.)

Some text has been imported only under CC-BY-SA and CC-BY-SA-compatible license and cannot be reused under GFDL; such text will be identified either on the page footer, in the page history or the discussion page of the article that utilizes the text. All text published before June 15th, 2009 on Wikipedia was released under the GFDL, and you may also use the page history to retrieve content published before that date to ensure GFDL compatibility.

If you are unwilling or unable to use the Creative Commons Attribution/Share-Alike License or the GNU Free Documentation License for your work, use of Wikipedia content is unauthorized. Small quotations of Wikipedia content, with its source attributed, may be permissible under the "fair use" clause of US copyright law. See Wikipedia:Citing Wikipedia for information about the proper citation of articles. No permission is needed to create a hyperlink to Wikipedia or its articles.

Images used in Wikipedia may have their own, completely independent licensing scheme. Looking at an image's description page by clicking on the image itself should ideally tell you the copyright status of the image. Many images are either in the public domain or licensed under copyleft licenses (such as the Creative Commons Attribution/Share-Alike License), but many are copyrighted and used on Wikipedia under the "fair use" clause of US copyright law.

Something to remember too, is that WIkipedia entries are subject to change, particularly new data, so it's not necessarily reliable.

Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.