This is probably going to be useful! I’ll try it out in the future and give feedback. 
I personally think it should be ROS-independent/standalone, even if it’s only used with ROS, because it adds an unnecessary layer. For example, having it under ROS makes the commands quite verbose. For help, rosrun catmux create_session -h is quite long (all catmux commands start with rosrun catmux create_session, so it could really be simplified to just catmux).