The "source code" of a software package is the form that is preferred for making modifications to it. This form varies with the nature of the software package. Generally, it is the form originally edited by the software's author.
The source code includes all machine- or human-readable instructions necessary to generate and install the form of the software that is to be executed on a computer system. It need not include software that is made available in source code form elsewhere.
To be included in this distribution, every part of a software package must be available in source code form. The binary packages generated from the distribution's source package must be derived directly from the package source code.