I've said this before, and it only bares more attention after the whole EULA nonsense.
Any plugin, mod, or resource that uses Minecraft or Mojang's IP as covered by their ToS and EULA may not be used commercially. This is quite clear, and the line here is not gray.
Premium Resource Section Not Completely Legal
Any plugin, mod, or resource that uses Minecraft or Mojang's IP as covered by their ToS and EULA may not be used commercially. This is quite clear, and the line here is not gray.