It is a multi-emulator emulating the Atari 2600, Commodore C64, C128 and Vic20. The many changes are visible on the main page of the official site. Note that the term "NewUI" has been removed as it no longer has any interest.
Z80 IN/OUT accesses RAM from $d000-$dfff for locations $0000-$1000 only when RAM bank 0 ismapped in.
Fixed bug with monitor when banking in ROMusing bank command for c128