4.2 Who wrote all that software?

For each package the authors of the program(s) are credited in the file /usr/share/doc/PACKAGE/copyright, where PACKAGE is to be substituted with the package's name.

Maintainers who package this software for the Debian GNU/Linux system are listed in the Debian control file (see What is a Debian control file?, Section 6.4) that comes with each package. The Debian changelog, in /usr/share/doc/PACKAGE/changelog.Debian.gz, mentions the people who've worked on the Debian packaging too.