I'm not an expert, so this comment is worth less than $0.02, but as a quick first reply
OBS is for compositing video (ie putting together multiple sources into one video)
For already existing videos, I can't see why one would use OBS. YouTube might be one option, though I've not researched/not aware of such security options as to check a subscription/membership roster for a group video (might exist, and I'm just not aware). Part of your answer will depend on how careful your content owners wish to be about link/content being shared outside who they think should be authorized. Such identity mgmt gets real complex, real quick, depending on desired security level.
Sound like you are looking for a hosting environment for their videos, and a means to control access. This could be their own website, but with bandwidth consumption implications (and end user support, codecs, etc). There are other video hosting providers that might be a better bit
