There’s an official integration, Hue Connect. It’s not an open API, it was officially developed between Smartthings and Phillips. When you use the smart things mobile app and go to add a device, one of your choices is a Hue bridge. Adding that automatically installs “Hue connect,” and brings in any devices connected to it of a type that Smartthings recognizes. After that, those devices are available for use through all the regular SmartThings control channels. That’s really all there is to it.
There are some community members who have written their own device types which would expose more of what’s available. You might find those interesting. In particular flexi lighting by @infofiend . You can find information about it in the community-created smart apps category under projects. The following is a clickable link.
The hack that’s being discussed in the thread we’re in now is something altogether different. It’s not code that allows smartthings to control Phillips hue bulbs through a bridge.
Instead, it uses the hue bridge emulator, software that Phillips provides for developers to test apps, and spoofs a real bridge so that HomeKit will be fooled into working with it.
Use of the emulator software in this way is a clear violation of the Phillips developer TOS, but if you yourself didn’t commit to that TOS, you’re probably not prohibited from using it once it’s out in the wild. Whoever originally released it may be.
But you certainly don’t need this hack to have Smartthings work with a Phillips bridge. It already does. You only use it if you want HomeKit to work with nonhomekit devices.
The following is the official smartthings support knowledgebase article on connecting to Hue:
https://support.smartthings.com/hc/en-us/articles/200848024-Connecting-Philips-hue-to-SmartThings