I think Unity’s Mono scripting language also supports JavaScript. There are a number of Hive libraries for JavaScript, so that might be easier. But I haven’t tried myself.
The API documentation for reading and writing data to Hive is well documented on developers.hive.io.
They have stepped away from JAvascript and Boo (Python Derivative) and it is only C# now. That is okay. I don't mind converting it.