Wirecast has been around since the mid-2000s and has a very similar feature set to OBS. It is lacking in some areas and ahead of the curve in others (Wirecast has GPU-accelerated scene preview thumbnails instead of OBS’ flat text list). VMix is another successful proprietary desktop streaming software. You could also probably add the OG, TriCaster, to the same list as it solves many of the same problems (video switching on commodity PC hardware, real-time layering/compositing, desktop capture, etc) but is married to NewTek’s hardware.