Hello Ole, seeking to clarify your latest. My understanding is that pgplot5 is in Debian now under Debian Policy section 2.2.3, in the non-free archive area.
Also, libpgplot-perl is in Debian now under Debian Policy section 2.2.2, in the contrib archive area for Stretch, and main for later releases. So I don't think the license of pgplot is the main problem or indeed a cause of the problems described here. The problems can be traced to the changes in libpgplot-perl, so I also suggest this bug be reassigned to that package. I agree that you should reassign it. I don't think the problems in this bug can be efficiently fixed in Giza, when compared to the effort required to change libpgplot-perl. I suggest you change the Giza source package Description from "drop-in, modern replacement" to "mostly compatible, modern replacement". If you'd like another bug for that, let me know. I agree a license change to pgplot would help, but it hasn't happened yet. Let's not make the perfect the enemy of the good. A risk to Debian is to create an unnecessary derivative distribution for a substantial group of users. This group of users has a very slow deployment cycle, so it can take longer than a Debian release or two for critical issues to arise. Thank you for your time on this bug.