China’s AI ecosystem has one defining difference from Silicon Valley: it’s embrace of open source. While America’s biggest companies race to build ever more powerful systems and insist only they can control them, Chinese labs have been giving the technology away for free.Open source — making a model available for anyone to use, download and build on — once seemed a niche, nerdy topic that no one besides developers cared about. But when a new technology is driving trillions of dollars of investments and leading to immense concentrations of power, it offered an antidote. That’s part of the reason I’ve…