HTC just pushed the Android 7.0 Nougat update to the unlocked version of its flagship, the HTC 10. As an owner of a 10, I can confidently say that the update is pretty well-done. As a natural next step, HTC has now also released the 7.0 kernel source code for the 10.
Since only the general unlocked model of the 10 has officially released the Nougat update thus far, that's the only model that has had new source code uploaded. If you couldn't tell from the relatively minute 219MB file size, this is not a custom ROM or something you can flash; it's what developers need to make ROMs and mods.
If you're a developer for the HTC 10, get to work!