NUT provides several libraries, to ease interfacing with 3rd party programs:

External applications, such as asapm-ups, wmnut, and others, currently use it. But it is also used internally (by upsc, upsrw, upscmd, upsmon and dummy-ups) to reduce storage footprint and memory consumption.

The runtime libraries are installed by default. However, to install other development files (header, additional static and shared libraries, and compilation helpers below), you will have to provide the --with-dev flag to the configure script.