Long story short... I was able to get the obs studio virtual camera working with FreeBSD.
The long story is that after trying OBS-Studio on FreeBSD, I immediately notice the virtual camera was not available. I did some research, and the issue was solved in the past but for whatever reason patch that enabled the virtual camera was removed from the port tree. I file a bug in FreeBSD bugzilla, and also email the maintainer of the port with the bug information.
To my surprise the maintainer responded my email and patch OBS-Studio. Now virtual camera is available for everyone using FreeBSD. 馃檪
This is how you make it work.
1.Using your terminal navigate to obs-studio port directory.
2. run "make config" and uncheck the browser option and hit enter.
3. run "make install clean"
4. run "webcamd -c v4l2loopback"
5.start obs-studio (The virtual cam button should be present now)
6. Start virtual camera.