There also exists a compatibility layer to be used with as an LD_PRELOAD, but I can’t find this library on my Ubuntu 14.04 : https://beeznest.wordpress.com/2011/07/02/adobe-flash-and-v4l2-webcams/
I will investigate on this and the previous, later, and will tell if one or the other works
This one works, but only with Firefox, using /usr/lib/i386-linux-gnu/libv4l/v4l1compat.so (exactly LD_PRELOAD=/usr/lib/i386-linux-gnu/libv4l/v4l1compat.so firefox). One may have to use another path (run a find /usr -name v4l1compat.so to get yours). Works with Firefox, but still not with Opera, no picture, while at least, it prompt me for access right to the camera, so that's still a step further.
Note as Flash does not work with Opera, I tested the webcam with Opera, on a website which does not rely on Flash: opentokrtc.com/ (I tested Firefox on the same too).