I don't really know how deep game data integrates with game engines, but if the game data is just non-functional (no scripts, fonts, manuals, executables, and so on) then any correctly licensed game data that allows the user to at least share the work for non-commercial purposes will be just fine.
But if the game data happens to have functional data then there's room for software freedom and, personally speaking, simply asking for DRM-free game data won't solve the moral, and perhaps even ethical, dilemmas that will arise.
