According to this article over on pcgamer.com, Baldur's Gate Enhanced Edition is being pulled from vitual shelves due to "contractual issues." Trent Oster, President of Beamdog/Overhaul said:
“We recently removed Baldur’s Gate: Enhanced Edition from sale on Beamdog and the Apple App Store. We’ve taken this step at our publishing partner’s request as we attempt to resolve a number of contractual issues.”
At the time of the article I can verify that BGEE was still up and running on Steam, however at the present time, Steam has been going up and down. Whether that is directly related to the potential removal of BGEE is unclear.