Good news everyone,
there were complaints that Software Collections don't have any upstream
location. I was hoping we could use Fedora as an upstream. But most
probably we won't be able to put everything from our project page 
Therefore, we were looking for different options. The new build system
COPR  should be soon able to build Software Collections. The content
could be transfered to softwarecollections.org
. I guess it takes at
least month of work.
At first we need some generic directory not related to any vendor
(Fedora, RHEL, ...) where we could install upstream collections.
Upstream community of scl-utils and COPR agreed on location /opt/sclo,
but I would be fine with something similar like /opt/scl.
Looking forward to your opinions,