Thanks for linking this. I was on the fence on what I've been hearing about owncloud/nextcloud.
I feel the Nextcloud guy (Jos) did extremely well defending against 3 unprofessional interviewers that degraded it into a rant session. Afterwards they go back and recant things they said during the interview saying maybe they were too harsh because he was late, etc. Then from a high horse they preach about "responsibility" in software development as if they are saints and have flawless work.
So, looking at this on the whole I've a ton more respect for Jos and Nextcloud willing to even speak to randoms as this is literally, the type of soykaf show you will see. This was not a candid interview, 3 rabid dogs on 1 man and he handled them well.
Jos and Nextcloud honestly didn't have to give a soykaf about their users but it turns out they do have a sense of responsibility even if the software they made is under a different flag (Owncloud). I'd rather see a bunch of angry hypocrites ranting about soykaf they got for free than another Wannacry-tier debacle. (Owncloud 5 was free and a very old version at that, windows XP of nextcloud)
So, they did what was necessary to get these systems patched. They left it with the shadow server people and they took action accordingly which was warn the ISP. Major sec vulnerabilities aren't something to publish on a blog post and tracking down users without contact info is pretty impossible, let alone getting them to apply an update.
I don't know all the little details and but based on this interview alone, I'd still use Nextcloud over google drive/dropbox/etc.