FIrst of all, in RPM package management, what decides if a repo is compatible or not? Coming from Debian were were always told NOT to mix Ubuntu and Debian repositories. In practice there is usually nothing wrong with doing this (if you are not running a server and dont need rock solid stability 100% of the time), as long as these are for extra apps or custom stuff, rather than core system stuff....If you add Debian Testing to Ubuntu it will ruin your system. If you add the custom repos for Backbox Linux to Mint Debian it will work ok for the most part. Sometimes you just have to run Synaptic twice.
So how far does compatibility go? Are you still compatible with Mandriva repos? Can you go farther and add other RPM repos (just apps, not system repos) from Fedora or Suse or Slackware? I am not asking if you SHOULD or if its good for stability. I am asking if you can in theory add the repo to software sources and try to download a package.
Next question: Are there any good security pen-test or privacy repos for Mageia? Any for Mandriva or any others? Any good multi-media or non-free repos?