AmigaOS 4, (abbreviated as OS4 or AOS4), is a line of Amiga operating systems which runs on PowerPC microprocessors. It is mainly based on AmigaOS 3.1 source code developed by Commodore, and partially on version 3.9 developed by Haage & Partner. "The Final Update" (for OS version 4.0) was released on 24 December 2006 (originally released in April 2004) after five years of development by the Belgian company Hyperion Entertainment under license from Amiga, Inc. for AmigaOne registered users. During the five years of development, purchasers of AmigaOne machines could download pre-release versions of AmigaOS 4.0 from Hyperion's repository as long as these were made available.
On 20 December 2006, Amiga, Inc abruptly terminated the contract with Hyperion Entertainment to produce or sell AmigaOS 4. Nevertheless, AmigaOS 4.0 was released commercially for Amigas with PowerUP accelerator cards in November 2007 (having been available only to developers and beta-testers until then). The Italian computer company ACube Systems has announced Sam440ep and Sam440ep-flex motherboards, which are AmigaOS 4 compatible. Also, a third party bootloader, known as the "Moana", was released by Acube on torrent sites; it allows installation of the Sam440ep version of OS4 to Mac Mini G4's. However this is both unofficial and unsupported as of today, and very incomplete, especially regarding drivers. During the judicial procedure (between Hyperion and Amiga, Inc), OS4 was still being developed and distributed. (Full article...)