Just like the drivers for say some graphics cards/etc. some portion of the Myriad X will be in binary only.

So part of our effort will be writing the support code for loading these binaries, and also producing these binaries based on customer interest.

That said, all the portions of interacting with the Myriad X as one already does now through NCS2 with OpenVINO should be the same flow, or very similar (open source, modifiable, etc.).  

Specifically (but potentially not limited to this), the hardware and firmware for the stereo depth calculation is non-public, so the stereo-depth capability will be provided as a binary download.

If/as more functions which are not covered by OpenVINO (and hopefully OpenVINO soon simply covers stereo depth as well, which would be a great possibility), we can respond by implementing these and releasing binaries.

All that said, OpenVINO is a very promising platform, and is quickly adding great capabilities - so there's a chance that these initial limitations may disappear soon.