For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:M0ses:branches:OBS:Server:Unstable/16.0/home:M0ses:branches:OBS:Server:Unstable.repo
zypper refresh
zypper install obs-server
For 15.7 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:M0ses:branches:OBS:Server:Unstable/15.7/home:M0ses:branches:OBS:Server:Unstable.repo
zypper refresh
zypper install obs-server
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:M0ses:branches:OBS:Server:Unstable/15.6/home:M0ses:branches:OBS:Server:Unstable.repo
zypper refresh
zypper install obs-server