scribus is developed on a secret svn server where only the team has access...
luckily, somebody has sneaked in a sync script that mirrors everything they do to this server:
svn co svn://scribus.net/trunk/Scribus scribus
i was annoyed that everything was hidden behind that svn encryption and made a solution that converts everything into the open source world:
git clone
https://github.com/scribusproject/scribus.gitand
https://gitlab.com/scribus/scribusthe secrets you are looking for are hidden in here:
https://gitlab.com/scribus/scribus/blob/master/scribus/pdflib.hirony off/>
of course, scribus is open source...
but getting scribus to run without an x server will be hard. but it's not an impossible task.
most poeple have found it easier to run scribus under Xvfb.
but i would welcome every effort done to get scribus to run without any GUI. theoretically i really think that it should be possible! and i would probably even improve the GUI code and remove lot of bugs!
finally, creating an application that produces a PDF from SLAs is probably not triivial but not that hard either: you will have to fake (and reimplement) all the calls to the outside world, so that they do not depend on a GUI (and, possibly, find a way to get the changes back into the main code, so that you don't have to maintain it).
if i get paid for that, i would not mind doing it...
there are other possible solution to make your conversion workflow faster and i would not mind to do some consulting for it : - )
ciao
a.l.e