Open source hardware: The problems and promise

Is open source hardware a thing? No, I’m not asking whether open source hardware projects exist. Of course they do, whether high-profile projects like Open Compute (from Facebook) or lower-profile projects like the Homebrew D-STAR Radio (for amateur radio enthusiasts).

No, what I mean is, have any open source hardware projects taken off similar to Kubernetes, Apache Kafka, or Linux? And, perhaps just as interestingly, does an open source hardware project have to reach that level of prominence in order for it to be useful?