http://wikimediafoundation.org/wiki/Job_openings/Code_Maintenance_Engineer

The core purpose of this job is to review and resolve bug reports, enhancement requests, code changes and extensions relevant to Wikimedia's free education projects, and to implement systematic testing procedures. This is a very hands-on role for an experienced software engineer who is interested in achieving high impact in a fast-paced environment with a public benefit mission. If you have existing development experience with MediaWiki, that's a huge plus. :-)

We will take remote applicants into consideration, and we'll also consider supporting relocation of the right candidate - our preference is for this person to be based in the San Francisco office of the Wikimedia Foundation.