backintime: Where are the sources from?

[c.buhtz at posteo.jp]

Hello,

as a (becoming) upstream maintainer try to better understand the logic 
behind packaging in Ubuntu.

I learned that distros like Debian, Manjar, Arch, etc taking the source 
for a package directly from upstream.

Let's take the universe package "backintime". Where do you get the 
sources? Or better asked: How can I know myself?
Do you take them from ubstream (the github repo itself) or do you take 
the source package from the Debian archive? Or I also found deb-files on 
launchpad. Maybe the latter is just für 3rd-party PPA and 
official/community Ubuntu?

So I am a bit confused here.

Thanks in advance
Christian Buhtz