It appears that forum.niftools.org is down (with a 502) and the SSL certificate expired on 10/2018. Please consider updating the site (or even removing the reference) if it is no longer valid to point there. If it helps, Let's Encrypt (certbot) is a good solution for such sites, if maintaining a 'classic' certificate is too costly or too much of an administrative burden.
I was uncertain where to put this issue, and ultimately decided on here as this repository appears to be for the main website, the closest fit.
It appears that forum.niftools.org is down (with a 502) and the SSL certificate expired on 10/2018. Please consider updating the site (or even removing the reference) if it is no longer valid to point there. If it helps, Let's Encrypt (certbot) is a good solution for such sites, if maintaining a 'classic' certificate is too costly or too much of an administrative burden.
I was uncertain where to put this issue, and ultimately decided on here as this repository appears to be for the main website, the closest fit.