That link says:
dfsg refers to a package that has been modified for compliance with the Debian Free Software Guidelines.
The Debian changelog for that package is at
https://metadata.ftp-master.debian.org/ ... _changelog
It seems to me (from the very narrow perspective of examining this one package only) that 'dfsg' is a
flag indicating that the package has, at some point in its Debian maintenance history, been subject to some modification for DFSG compliance. That is, it is separate from the attached serial numbers. For instance, if we look at the changelog between versions '2.0.2+dfsg1-5' and '2.0.2+dfsg1-6':
* rules: disable activec for ppc64el build (Closes: #770670)
-- this is clearly an optimization change (probably to restrain an overly aggressive compiler which breaks the code). It has nothing to do with licenses. Thus, 'dfsg1-6' doesn't mean 'waypoint 1.6 in the history of this thing's conversion to DFSG compliance', but rather 'DFSG flag is present; by the way, this is version 1.6 of our work on the upstream package version 2.0.2'.
The flag first appeared between versions '2.0.0~rc1-1' and '2.0.0+dfsg1-1'. The changelog for that has several notes, but I think this is the one which provoked 'dsfg':
- Remove from debian/copyright files that are now filtered out when creating the orig.tar
-- as fiddling with copyright statements would fall squarely under the domain of DFSG.