Software is transforming industries from agriculture to automobiles. So it is fitting that the latest multibillion-dollar company in Silicon Valley is GitHub Inc., which says it hosts the largest community of software developers and projects on the Web.

GitHub this week raised $250 million from prominent Silicon Valley venture firms, the company said. The infusion raised its valuation to about $2 billion, according to sources familiar with the matter, and brought the San Francisco company’s total funding to $350 million.