The directory dfsg stands for: Debian Free Software Guidelines, see https://en.wikipedia.org/wiki/Debian_Free_Software_Guidelines
To build an official Debian package, one needs to check thoroughly than every source file shipped in it is distributed under a DFSG-free license, and give proper credit to the authors inside the file debian/copyright which will be included in the debian source package.
Some parts of the official source tarball for WIMS are not DFSG-free, i.e., they may be free enough for the main concern of a random Wims administrator, allowing him to run the server legally, but they are not free according to the Debian Free Software Guidelines.
Examples of non-dfsg-free parts include packages including third-party components with non-free licenses: a non-commercial clause makes a license non-free, as well as a clause stating that the only legitimate use is for education. More subtle non-free licenses can be the "good, not evil" license authored by Douglas Crockford; even if it may be considered as a joke, it entails a legal instability which is refused by Debian developers. See https://en.wikipedia.org/wiki/Douglas_Crockford#.22Good.2C_not_Evil.22.
Also, every source file must be human-readable. For the sake of efficiency, many javascript files are compressed or "uglified" in order to use less bandwidth. If a javascript is compressed, minified or "uglified", it cannot be considered as a source file any longer. If so, it must be removed from the source package, and the source file yielding it must be included, eventually with some way to generate the compressed file upon compilation of the source package.
README.md
: the source file for this informationREADME.html
: this information in HTML formatMakefile
: a script for the "make" command, which strips non-dfsg
parts, and adds eventually third-party non-obfuscated sources for
javascript files.