I have just installed a recent distribution of MediaWiki and PHP, and the reCaptcha extension. In order to do this I had to use a different machine (dynamo.iro.umontreal.ca) and copy all the pages from the old wiki to the new wiki.
When a page edit is saved a visual captcha will now appear to make sure the edit has been submitted by a human user.
Please let me know if you find broken links, missing information, or other issues.
Marc