The subject of third-party repositories for Mageia4 is a touchy one for some people. For the maintainers of a distro, they feel that third-party repos cause compatibility problems and the packages are not subject to adequate. The third-party maintainers believe that they are maintaining either specially modified packages useful to their members or packages that the main distro cannot, for legal reasons, maintain and distribute. Both are correct.
If you need a package offered by a third-party repo, then by all means use it carefully. If not, don't even add the repos to your local repositories.
For Mandriva, the PLF at plf.zarb.org and MIB at PianetaLinux.org provide those services. For Mageia4, it looks like BlogDrake.net is taking the lead. They provide repositories for Mageia1 through Mageia4.
You may add the appropriate Mageia4 repos as root using the commands below: (NOTE: the BlogDrake site appears to be down at this time)
Mageia 4 urpmi.addmedia --wget --distrib ftp://ftp.blogdrake.net/mageia/mageia4/x86_64 urpmi.addmedia --wget --distrib ftp://ftp.blogdrake.net/mageia/mageia4/i586