The SDK is a fixed, free component when purchasing a device.
It comes with the source code of the application program (in VB.net) and a LabView VI with the basic functions of the instrument. A description of the communication with the devices and a list of the commands used is also included.
For some devices (currently LDD100, LIV120 in preparation) there is a dll file (library file) with documentation and exemplary applications in VB.net and LabView.