[api] Bloomberg Open API

This API has been available for a long time and enables to get access to market data (including live) if you are running a Bloomberg Terminal or have access to a Bloomberg Server, which is chargeable.

The only difference is that the API (not its code) has been open sourced, so it can now be used as a dependency in an open source project for example, without any copyrights issues, which was not the case before.