MiNT ("MiNT is Now TOS") is a free software alternative operating system kernel for the Atari ST and its successors. Together with the free system components fVDI (device drivers), XaAES (GUI widgets), and TeraDesk (a file manager), MiNT provides a free TOS compatible replacement OS that is capable of multitasking.
MiNT was originally released by Eric Smith as "MiNT is Not TOS" (a play on "GNU's Not Unix"). Atari adopted MiNT as an official alternative kernel with the release of the Atari Falcon, slightly altering the MiNT acronym into "MiNT is Now TOS". Atari bundled MiNT with AES 4.0 (a multitasking version of GEM) under the name MultiTOS. After Atari left the computer market, MiNT development has been continued by a core of volunteers. Nowadays the official name has been changed to "FreeMiNT" upon request by Eric Smith. The reason for this was to distinguish it from the versions that were released by Atari.
There are several distributions, most notably the RPM-based SpareMiNT as well as the Debian GNU/MiNT porting effort.
Geneva The only known AES project from the US was contributed by programmer Dan Wilga of Gribnif software. The initial aim of Geneva was to provide a multitasking AES for users of TOS, but since TOS itself did not host any multitasking capabilities this only allowed for co-operative multitasking. The first release of Geneva back in June 1993 instead allowed all Atari users to multitask their GEM applications without using up much at all of their precious RAM. It was a commercial product, often bundled with the highly regarded desktop replacement NeoDesk. Geneva could however be run together with MiNT, then offering true pre-emptive multitasking. While this combination initially was not very stable, the last release helped improve that situation a lot.
MiNA Germany had always been an Atari stronghold so it was not surprising that most Atari software development was happening here. One of the projects to create a new AES was initiated by programmer Martin Osieka. He had previously created WINX which was a TOS extension that both provided some bugfixes as well as offered some nice new features, some of which was not yet seen even in the last AES 4.1 from Atari. To cover the need for a new user interface for MiNT, Martin started working on a project called MiNA. Unsurprisingly, this was an acronym for "MiNA Is Not the AES". While enthusiastic Atari magazines had stated that over 50 developers had teamed up helping Osieka with the project, things came to a grinding halt when his Atari machine broke.
N.AES Also located in Germany, in 1994 Jens Hiescher started a similar project that was originally named Signum. This project progressed so nicely that German company Overscan bought it and released it commercially under the name N.AES. N. AES had its final release in the late 90's and at the time it had become a very robust AES for MiNT, and included a number of innovations compared to the ancient AES 4.1 from Atari. To mention a few of them, users now had access to keyboard shortcuts for window gadgets, possibility to hide applications, and optional hiding of the menu bar. The latter saved the user some screen space, as the menu bar would disappear when the mouse was moved outside of its limits.
oAESis Another project was started 1995 in Sweden, by Christer Gustavsson. The project was oAESis, and it did actually progress into a somewhat usable project. Even if this AES looked promising enough, the end product never reached a fully mature and stable state. After some time, the project was incorporated within a bigger plan. OSIS was an effort to create an Atari TOS/GEM compatible environment for Linux, constisting of the subsystems oTOSis (TOS/MiNT replacement), oAESis (AES replacement), oVDIsis (VDI replacement) and oFBis (a framebuffer library). On a funny side note, the name OSIS is also Swedish slang for "bad luck". The project progressed until around year 2000, when it seemed like the involved programmers were losing interest and time to keep things going.
XaAES Also started in 1995, there was XaAES. The UK programmer Craig Graham was frustrated that there was no decent user interface that could take advantage of the power of the pre-emptive multitasking in MiNT.
MyAeS is another AES project, it was started in May 2003 in France, by Olivier Landemarre. First public version was available in February 2004.