These are converters/adapters - they can only be used on top of existing built-in(non-removable) lenses, so any FLIR Ex and Exx camera, as well as the T4xx and earlier, will work(with DIY mechanical adapters). The T6xx cameras use newer, differently-mounted lenses.
However, the lenses themselves contain calibration data and an integrated temperature sensor, which is crucial to temperature measurement due to the rather sloppy performance of Germanium over different temperatures, as well as having an additional emitting optical element(remember, above 0K) in the optical path.
I suspect they're either I2C or SPI, so it should be fairly easy to read out.