Thanks a lot for all the encouring feedback! I'm glad I could help (for once
Okay, here's the bit regarding OS 3.5/3.9. Probably the least interesting for most of you, as these are "old" products.
I think that should cover most of it, unless somebody finds some of his questions unanswered ?
AmigaOS 3.5
In 1997, the US-based PC distributor Gateway2000 bought Amiga Technologies. They were mainly interested in the patents related to the Amiga, but when they found out that there was still a big and demanding community, they decided to do something with the technology.
Gateway established Gateway-Amiga Inc., located in Seattle. Amiga Inc. was intended to be the Research&Development center, while the German-based Amiga Technologies should have acted as the marketing and distribution division.
In the following two and a half years, Amiga Inc. made lots of announcements (some people counted thirteen), none of which came true. It seems they were constantly stopped by their parent company, which had no real clue what to do with the Amiga.
One of those announcements was AmigaOS 3.5. A quite ambitious project, with several key enhancements. But after a few months, Amiga Inc. started to lay off developers working on the update and the progress reports were removed from the web site.
At that point, the German software company Haage&Partner started to apply for a license to develop OS 3.5 on their own. In early 1999 Amiga Inc. finally agreed and the update was officially announced (again).
When OS 3.5 was finally released in September 1999, the reactions were quite mixed. Due to financial reasons, the update did not include new Kickstart ROMs. This severely limited the possibility for major enhancements. There are a lot of new features in OS 3.5, but most of them are not yet used to the full extent. H&P were completely new to the OS business and the installation procedure aswell as the overall stability of the OS were somewhat lacking. Nevertheless, OS 3.5 finally removed some long standing problems and included lots of third party patches and extensions that had established over the years into the OS.
AmigaOS 3.5 is still pure 68k code. Amiga Inc. was not interested in a PPC port. OS 3.5 was a financial loss for Amiga Inc.
Amiga OS 3.9
In 2000, when Amiga was sold to Amino Inc. and was now an independent company again, H&P (and several other commercial developers) approached them over and over again, to finally get the permission to do a PPC native version of AmigaOS. Amiga Inc. didn't have any plans with the existing Amiga technology and blocked such attempts.
But when Amiga realised that they would not be able to release various announced AmigaDE-related products on time and they were evaluating the need for a PPC AmigaOS4 anyway, the changed their mind and gave H&P permission to do another update for 68k-based Amigas. H&P had already done a lot of work for OS 3.9, so they could release it only four weeks after it was announced, in December 2000.
AmigaOS 3.9 is best described as "OS 3.5 done right". Most of the functionality that was introduced with v3.5 is now used to its full extent (multitasking Workbench, powerful filetype recognition...). It's described as "the most stable AmigaOS version since 2.0" by most people using it. Still, it didn't include new Kickstart ROMs and no major enhancements. That's why many people refer to it as "OS 3.5 with a lot of Aminet tools thrown in". But the overwhelming majority of OS 3.9 users is quite happy with the update.
AmigaOS 3.9 is still pure 68k code. It is the final OS update for 68k-only Amigas. Future versions of the Operating System will only run on PPC processors.