In 2015, car-and-rocket man Elon Musk joined with influential startup backer Sam Altman to put artificial intelligence on a new, more open course. They cofounded a research institute called OpenAI to make new AI discoveries and give them away for the common good. Now, the institute’s researchers are sufficiently worried by something they built that they won’t release it to the public. The AI system that gave its creators pause was designed to learn the patterns of language.