Mike, the particular Biotar in question is a cine lens, made for the 16mm format though apparently 35mm-compatible too. I've seen 'em on eBay, sometimes converted to M mount. I have one of the Zeiss 58/2 Biotars in M42 screwmount and a friend has a 75/1.5. These are both SLR lenses and can be adapted to various modern cameras.
-Dave-