BGLIB is a software library used by the host system when controlling Silicon Labs' Bluetooth® modules and dongles from an external host system (microcomputer or PC).
Since it is provided in C source code, it can be ported to various host systems, from inexpensive MCUs to systems that run on Linux, Windows, and OSX.

Please also refer to the SiliconLabs community site for the difference between BGAPI and BGScript.