You can find information about C++ module here.
You can create Linuxconf modules using either bash (the shell), Perl or Python. Bash and Perl are handled by the shellmod module. Here is the help screen describing how it works. Shellmod is intended for fairly simple module. It is possible to create something useful in 10-20 lines of shell scripts. Check it out!
The Python support is handled by the pythonmod introduced in Linuxconf 1.23r1. The module is part of the core distribution. Unlike shellmod, pythonmod is a complete binding. It provides access to many functionalities of Linuxconf APIs, including CONFIG_FILE, PRIVILEGES and the user interface.