Nobody stopped them; they were just busy doing other things that made the effort worthwhile. It's worth keeping that in mind, to make sure that competitive cla

Nobody stopped them; they were just busy doing other things that made the effort worthwhile. It's worth keeping that in mind, to make sure that competitive claims about performance don't drown out proper credit for the true innovators. Note that I'm not saying anything is wrong here. Reimplementations of existing ideas are a time honored tradition, and often lead to their own innovations. Linux was a reimplementation of UNIX, and seems to have been good for a lot of people. Most web servers and browsers are reimplementations of things that had existed previously. From compilers and databases to filesystems and hypervisors, a lot of software we all rely on today - especially in open source - is a reimplementation of something or other. I'm pointing out an opportunity, not a flaw.