Moeller has been involved in editing, contributing to and developing projects at the Wikimedia Foundation since 2001.
He joins from Netherlands-based Stichting Open Progress, the not-for-profit legal arm behind OmegaWiki, where he was chief technology officer.
He will now be responsible for leading the development and execution of Wikimedia's technical strategy and other projects and initiatives.
During his time at Stichting Open Progress, Moeller managed a team of developers for the implementation of OmegaWiki, and also provided hosting for several Wiki communities, including WikiEducator.org.
He has been involved with the Wikimedia Foundation since 2001 as an editor and contributor, and was instrumental in the launch of Wikinews and Wikimedia Commons.
As part of his fulltime joining, Moeller has resigned his post as board member of the Wikimedia Board of Trustees, and will join the organisation's staff in San Francisco.
Earlier this week, Jimmy Wales, founder of online encyclopaedia Wikipedia, unveiled a new community-oriented search engine, called Wikia Search, which allows members to rate search results and improve relevancy for other users.