For example, some packages have licenses which prohibit commercial distribution. Others can be redistributed but are in fact shareware and not freeware. Users are welcome to use and test these packages, but are warned about their state of readiness. These include, for example, Perl scripts, or pure documentation. Currently this is done mainly for Atari and Amiga computers, and also for some VME based industry standard boards.
Source code is included for everything in the Debian system.
Moreover, the license terms of most programs in the system require that source code be distributed along with the programs, or that an offer to provide the source code accompany the programs. Various indices, maintainers, Packages-master files, override files. Users shouldn't be using packages from here, because they can be dangerous and harmful even for most experienced people.