VirtualCam was already a thing, but only for Windows (not sure what is the backstory behind the more recent version being maintained by someone else; I think I'm using catxfish's version): https://obsproject.com/forum/resources/obs-virtualcam.539/
...then select "VirtualCam" from the Tools menu, and click "Start" to start sending images to the selected virtual camera. These virtual devices appear in eg. Zoom, so if you select it and enable video within the app, others will see 5 faces and Visual Studio Code having a conversation.
(Of course you can add more sources to the scene, aligning them appropriately, so you can have your face in the corner alongside the captured window.)
OBS has full desktop as well as window capturing capabilities, so if you only want to show the contents of a single window, you would add a "window capture" item to your scene: https://github.com/obsproject/obs-studio/wiki/Sources-Guide#...
...then select "VirtualCam" from the Tools menu, and click "Start" to start sending images to the selected virtual camera. These virtual devices appear in eg. Zoom, so if you select it and enable video within the app, others will see 5 faces and Visual Studio Code having a conversation.
(Of course you can add more sources to the scene, aligning them appropriately, so you can have your face in the corner alongside the captured window.)