More details on the history of Linux can be found the book Inside Linux by Randolph Bentson <bentson@grieg.seaslug.org> (see section Books for more information about this book).
Linux is a freely available operating system for PCs: to be more precise, it is one of many flavors of Unix. Linux is being developed on the Internet by several thousand people, first and foremost by Linus Torvalds <torvalds@cs.helsinki.fi>, who created Linux for the 80386 in 1991. Linux is being tested and used by many more (the total is thought to be in the hundreds of thousands, perhaps millions).
At the time, Linus believed that Linux was inherently Intel-specific. A few Amiga and Atari hackers were determined to prove him wrong.
The fun and success of Linux on Intel-based systems inspired Hamish Macdonald <hamish@border.ocunix.on.ca> and Greg Harp to port it to another platform: the Amiga. The first version released to the general public was 0.0.5. While 0.0.8 was current, a few enthusiasts ported that version to the Atari and the two versions were successfully merged with 0.9pl3 (this reads version 0.9 patchlevel 3).
After releasing 1.2.13pl3, Hamish handed the coordination over to Roman Hodek <rnhodek@informatik.uni-erlangen.de>. Starting with Hamish's unfinished 1.3.20 port, Jes Degn Sørensen <Jes.Sorensen@cern.ch> started to work on integrating the m68k stuff into 1.3. With 1.3.94 the majority of the m68k stuff was put into the official kernel tree. Work continues to integrate Linux/m68k with the mainstream kernel.
The present 2.0 series releases are of ``production quality'' and are suitable for general use on the Amiga, Atari and supported Motorola VME (162, 166 and 167) platforms. The versions of the 2.1 series are generally as stable as their counterparts on Intel platforms (probably even more stable, as there is more testing between releases).
Here's the story about the beginning in Hamish's words:
I decided to port Linux to my Amiga for a variety of reasons. I have always had an interest in operating systems (my work is in embedded systems for telecommunications). After finishing my Master's thesis, I needed some project to keep me busy, and justify keeping my Amiga. Linux was just getting popular at the time, and I thought it would be fun to port it to my Amiga. So I did. Greg Harp and a few others had been talking for a while about porting Linux to the Amiga. They'd only got a little way into it when I got involved, bringing the work I'd already done myself....
And here about the port to the Atari in Roman's words:
I'm an old Atari user, but in some dark age of Atari, I also bought a PC... running only Linux, of course! Some time later, I noticed that there was a Linux for m68k (was a version about 0.06 or so), but learned that it was for Amiga only. Already at that time, I thought that it can't be that hard to port this to the Atari, but after some browsing in the sources, I gave up. I just didn't find a point where to start. But at least I subscribed to the MausNet newsgroup ``LINUX68K''. Several months later, in April '94, Björn Brauel posted an article there, that he has adapted Linux's head.S so it ran on his Falcon (until the first console output :-). I again was interested and asked Björn for the sources. In the next time, we two built some very basic driver, so we could at least see some output on the screen, and the kernel booted until the "unable to mount root". There was no HD driver yet... So I started to write a SCSI driver, and Björn went to IDE.
At that time, we heard that there was another group working on an Atari port. The most important members of this group were Robert de Vries and Andreas Schwab. They've never announced that they're working or how far they are, so we didn't know about them. And we communicated over the MausNet, not the Internet, so they didn't notice us... So we finally had two versions of an Atari port at the same time. Fortunately, we've mostly worked on different parts, so the merged version 0.01pl3 made a big jump in respect to what drivers were available.
The next story is about Martin Schaller: He also ported Linux to the Atari, starting directly from PC Linux, not from the Amiga version. (He didn't have a modem at that time, so no Internet, not even MausNet...) For that he worked totally on his own, he came very far and did a great job. In fall 1994, a German Atari magazine published an article about Linux/m68k. By this Martin heard that there were some more Atari Linux hackers and joined us.