www.nextcloud.org uses an invalid security certificate. The certificate expired on June 17, 2017 at 6:31 PM. The current time is June 18, 2017 at 7:22 AM. Error code: SEC_ERROR_EXPIRED_CERTIFICATE
.com is still okay.
PS: There is no specific category to report main website issues such as this. There sure are a lot of categories to sift through. 
The category for this could be “meta”. I didn’t know nextcloud.org, does it actually belong to the Nextcloud company? If I ignore the old certificat, anyway no webpage opens.
Good point about about whether it actually belongs to nextcloud.com or not. I just made the assumption it would be since it’s an open source project. Given that the domain registrations are private, I can’t really tell.
we own but don’t use it 
I think it should redirect but that hasn’t been done. At some point we’ll probably put the Nextcloud Foundation there - once we get around to setting that up…
Need help?
We have discussed a rough plan almost a year ago at the first meetup already, and follow-ups occasionally. Frank wanted to ask some universities and others for feedback before sharing the plan in public. I think he mostly hasn’t had time for this 
After that - well, it won’t be too much work.