Tilix is a GNOME 3 terminal emulator which utilizes the GNOME header bar. It is actively developed with the most recent commit a day or so ago. Here is the url for the github: https://github.com/gnunn1/tilix
I know you guys aren't fond of packaging so many programs that do the same thing but, Tilix is a very nice program that is in some ways better than the default GNOME Terminal.
Is it Open Source: yes
Link to source tarball/zip file: https://github.com/gnunn1/tilix/archive/1.7.1.tar.gz