Why is GOG's Zork I different from the free versions available online? (I have paid for the Zork Anthology collection)
The first I noticed was that the map layout is different.. There is no bank and many other things are missing?

The Bank of Zork is in Zork II as far as I know. Maybe you are referring to the original mainframe Zork (aka Dungeon) that got its source released a few (relatively short) years ago?

That was the original the developers created while still at the university. After that they founded Infocom and split that into 3 parts, Zork I-III (which also were expanded with some content not found in the mainfram version).