Wikipedia is known for serving humans' informational needs. Over the past decade, the encyclopedic knowledge encoded in Wikipedia has also powerfully served computer systems. Leading algorithms in artificial intelligence, natural language processing, data mining, geographic information science, and many other fields analyze the text and structure of articles to build computational models of the world. Many software packages extract knowledge from Wikipedia. However, existing tools either (1) provide Wikipedia data, but not well-known Wikipedia-based algorithms or (2) narrowly focus on one such algorithm. This paper presents the WikiBrain software framework, an extensible Java-based platform that democratizes access to a range of Wikipedia-based algorithms and technologies. WikiBrain provides simple access to the diverse Wikipedia data needed for semantic algorithms and technologies, ranging from page views to Wikidata. In a few lines of code, a developer can use WikiBrain to access Wikipedia data and state-of-the-art algorithms. WikiBrain also enables researchers to extend Wikipedia-based algorithms and evaluate their extensions. WikiBrain promotes a new vision of the Wikipedia software ecosystem: every researcher and developer should have access to state-of-the-art Wikipedia-based technologies.