Welcome to Amiga.org!
There are several places trying to invent a successor to the classic Amigas. MorphOS is based on the Quark microkernal and comes with MUI and Cybergraphics. AmigaOS 4 has the blessing of Amiga, Inc. and is being produced by Hyperion Entertainment in Germany. AROS is an open-source attempt at making a source-code compatible AmigaOS replacement for x86 PCs.
Get used to using emulators, though, because none of them are compatible with the custom chipset. You'll find yourself using WinUAE under Windows and EUAE under most other platforms to run the old Amiga software. Amiga-Forever comes with both since the live-CD boot is based on Knoppix Linux and the install to windows is based on WinUAE.
