With regards to legal permission, if you look at the source code for packages in their github repos, you will see they usually use a BSD license (at least all the packages I have looked at do). I'm by no means an expert in this topic and they may be some clauses I am not aware of (i.e. look into this yourself if it is a serious concern), but I do believe that means it is free to use for research purposes.
For simulation, I would suggest looking at RVIZ, Gazebo, and Stage. RVIZ enables you to visualize data within ROS, while Gazebo and Stage are simulation platforms (with Gazebo being the more complex of the two). These are the most common tools used within the ROS world, but there is too much information about these to present here so I suggest looking into them on your own.
If you follow the simulation section in the Turtlebot Tutorials it provides a pretty simple example of simulating a Turtlebot in Stage and Gazebo, which may be helpful.
One last note about your choice of planner: I've tested both the eband_local_planner and the teb_local_planner, both of which are based on the elastic band method, and have found the teb_local_planner to be far better. It takes time into account and considers multiple trajectories simultaneously, which is more suitable for dynamic environments (such as an airport). It is quite well supported and has some excellent tutorials, so I suggest looking into it.
