Which programming environments or APIs are available for the LEGO BOOST? Over the holidays I tried the following Python library:
https://github.com/undera/pylgbst but I couldn't get it to work.
Then again my knowledge of Python is very limited.

I'm more experienced with C++ or C#, is anything available for those languages?

As a general question, do you know of any programming environments or API's that can control the LEGO move hub and its peripherals from the LEGO BOOST set?
Boost and the other Powered Up components (the new City trains, the app-controlled batmobile, and WeDo 2.0) are controlled via Bluetooth. Any environment that can send bluetooth commands can be used to control these components.

There is a github page which documents some of the reverse-engineering that has been done and it links to several third-party Boost/PoweredUp programming libraries. I've used movehub, but there is another node.js library called node-poweredup which looks more complete.

Lego themselves have documented part of the BLE wireless protocol on github as well.