XaAES is a graphical user interface for the OS kernel FreeMiNT. MiNT (nowadays named FreeMiNT) is aimed at systems that are compatible with 16/32 bit Atari computers such as the ST, TT or Falcon. The combination of MiNT and XaAES is the natural successor to MultiTOS.
XaAES is a free AES (Application Environment Service) written with MiNT in mind, originally developed by Craig Graham (Data Uncertain Software) back in September 1995. Taken from the XaAES beta6, here is a snippet of the readme.txt in which Craig explains his motives for initiating XaAES: "After using MultiTOS, then AES4.1, I became frustrated at the lack of a decent GUI to use the real power of the MiNT kernel - X Window is all very well, but I can't run GEM programs on it. MultiTOS (even AES4.1) is too slow. Geneva didn't run with MiNT (and, having tried the new MiNT compatible version, I can say it wasn't very compatible - at least AES4.1 is quite stable, if a little slow). MagiC lives in a very fast, very small world all its own (no networking support, few programs written to exploit it)."