Current release: json-c-0.15
Best starting points: json_object.h or json_tokener.h You can also look at the tests in the tests directory for some examples.
One of the simplest examples is test2.c.
Note: for the most recent development docs clone the source and run:
sed -e's/@CMAKE_CURRENT_BINARY_DIR@/doc/' doc/Doxyfile.in | doxygen -Then look in the doc/html directory.