The Free Peoples of Middle Earth is basically all the humanoid species and populations not loyal to Sauron or Saruman. The idea that they are politically free in our modern sense does not really apply. Democracy is not really a widely held to governmental structure. Human Rights are also not widely recognized either. Basically, the main uniting principle for these factions are the enlightened absolutism model of government and the fact they form the core of the anti-Mordor coalition.