I try to keep slackel stable. What is maintained by me is slackel binary repositories.
On slapt-srcrc there are already these
SOURCE=
http://download.salixos.org/slkbuild/14.2/
SOURCE=
http://download.salixos.org/sbo/14.2/
SOURCE=
https://www.slackbuilds.org/slackbuilds/14.2/
Tried to add SOURCE=
https://github.com/Ponce/slackbuilds
gives an error after sudo slapt-src -u
Packages on slackbuilds.org are not all build under slackel. These source repos are not part of slackel maintained binary repositories which are checked and it is sure that packages there work in slackel. Also note that if user compile a package from source which already exist on slackel repositories system (slapt-get,gslapt) will try to update the package even its version is newer. slackel, slackware are priority repos in this order over packages user add by its own.
I try to keep slackel stable because i use it everyday and being stable is useful for me.
It is difficult to keep slackel stable, which based on current tree of slackware, where things change every day. To add another repo it will break system for sure and job needed will be huge. And i am sure users and me want slackel to be stable