Our current setup is that one macbook films and broadcasts the stream with our webcam, and the other is stationed at a different angle running resolume paired with a projector which is projection-mapped to our DJ stage. My mac's only thunderbolt2 port is occupied with the vga cable that goes to the projector. The projector has a vga out & the other macbook has 2 thunderbolt ports and one hdmi free.
We are using ChewTv and the app OBS to stream.
Basically the top one is mine running resolume and to the projector through its only thunderbolt, and we want to connect it to the bottom one so resolume can be another video source during our livestream.

The mac below is the broadcasting one with a webcam-in via USB.

Hope this makes sense so far, thank you in advance for any ideas!