Today's beta version (v.1.1.0.7) introduces support for stereoscopic streams when using external USB cameras.
This version also has initial MJPG support.
To use a stereoscopic stream you need to edit the settings .xml file. (Please make a backup first.)
Replace the part with the following lines:
Change the text "3D USB Camera" to the name of your camera.
Also change the resolution, Format and FramesPerSecond as needed.
To see what formats your camera supports, run the app once, then open the file "VideoStreams.txt", which it creates next to the executable.
Remove the "" part, up to and including the "" tag.
More instructions are here:
https://store.steampowered.com/news/app/1844610/view/4109043267624151513