Method of and system for watermarking application modules

A method of creating and using a software application module includes coding, by a developer, a software application module for extending a functionality of a main software application. The software application module is adapted to interface with the main software application using an application programming interface (API). The method further includes compiling the software application module to produce an executable software application module, determining if the developer is authorized to use the API, and embedding a watermark in the executable software application module if it is determined that the developer is authorized to use the API. The method still further includes executing the main software application, reading the watermark from a executable software application module, verifying if the watermark is correct, and executing the software application module if the watermark is verified as correct.