What kind of protection (copyright) do the Gazebo models have?

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I've created a Gazebo world using a combination of geometric models and meshes downloaded from here and I'd like to open source these worlds as part of a benchmark project so that people can use them to compare different kind of algorithms. Of course I don't want to get into troubles for copyright ownership so I would like to know if this is allowed or what type of restrictions are there. The benchmark project is an academic initiative that would be open and free.

Thank you