I have started my experiments with Philips Hue with white bulbs, and so far it looks appealing. I would like to go on and add some more interesting bulbs, namely Osram Lightify Tunable White. Googling hasn't helped yet: Do I need to buy an Osram Bridge too, or can I pair an Osram bulb directly to the Philips Hue bridge?
Old outdated information about EU vs US firmware. https://www.reddit.com/r/Hue/comments/42840b/howto_make_american_osram_lightify_bulbs/
The firmware is now combined into one compatible version. Try this, several people report they work: https://recoveringappleholic.wordpress.com/2016/01/23/how-to-get-lightify-to-work-with-hue/
I believe @DanielGriscom was talking out of turn and sharing his thoughts that were based off poor assumptions rather than research.
From what I understand the US Osram bulbs use Zigbee HA, not Zigbee LL like the Philips Hue bulbs. The European Osrams use Zigbee LL, so that's why there are compatibility issues in the US. I have been wanting to get my Osrams on a Hue bridge, but cannot seem to make it happen.