From the announcement:
The Wikimedia Foundation is committed to making knowledge of all forms freely available to the world. Beginning today, our new Open Access Policy will ensure that all research work produced with support from the Wikimedia Foundation will be openly available to the public and reusable on Wikipedia and other Wikimedia sites. We are pleased to announce this new policy at the 18th ACM conference on Computer-Supported Cooperative Work and Social Computing (CSCW 2015).
Source: Wikimedia Foundation adopts Open Access Policy to support free knowledge