From what I can see from using Haiku for a bit, it has the bazar community element from the open-source culture with its package management and ports system from Linux and BSD whilst being conservative with its design from its apps, UI, and SDK like macOS. Although I have tired it and its surprisingly "useable", the driver story is still a bit lacking. But from a GUI usability point of view compared with many Linux distros, it feels very consistent unlike the countless confusing interfaces coming from those distros.
Perhaps BeOS lives on in the Haiku project, but whats more interesting is that the real contender who learned from its failure is the OS that has its kernel named 'Zircon'.