[dba-Tech] MS GP (formerly Great Plains)

Does anyone use this software? I have an opportunity for a short-term
contract to write some custom reports from its database. IIRC, back before
MS bought it, GP was written against a Btrieve back end. I'm assuming that
after the acquisition, the BE was replaced with some version of SQL Server.
I've been cruising the GP site, but so far have not stumbled upon an answer
to this question. My guess is that prior to the MS acquisition SQL Server
was not the BE, but at some point it became the BE, replacing Btrieve or
whatever was the original BE.

Can anyone verify or refute my suppositions? Any info or links much
appreciated. I would love to get this gig, not least because it's in the
same building as my residence, so it's a one-floor elevator ride to go to
work LOL.

Arthur