Can we share flash on cameras of different manufacturers?

I'm researching on a Yongnuo YN565EX E-TTL flash. I read someone said it can be controlled by either a Nikon D90 and a Canon 60D. Does it mean it can be triggered wirelessly off camera by both cameras? BUT MORE IMPORTANTLY, does it work mounted on the hot shoe for both cameras? Or the built for Canon will only work on a Canon hot shoe and built for Nikon works on a Nikon hot shoe?

To make it simple for the rest of the world, get a (for) Canon flash to use on a Canon camera and get a (for) Nikon flash to use on a Nikon camera even if you intend to use the flash off-camera.

There are ways to "cross-use" the flash but due to trigger voltage differences, you may end up destroying the camera.

Off camera when set as a slave a flash is pretty much just a flash as long as it uses an optical trigger (another flash set as Master).

On camera, it is a different story. While you may get a Canon flash to work on a Nikon (or vice versa), you will lose the E-TTL ability. In other words you would need to set the flash power manually.