Dammy already said it... it is a little more complicated.
there are three "NG" OSs now
MorphOS using used PPC Macs
AmigaOS using new but expensive PPC hardware
Aros running on different platforms (hosted or alone)
AmigaOS (the OS) is developed and sold by Hyperion and they have cooperations with Acube and e-on that produce and sell the hardware
MorphOS is developed and sold by the MorphOS team and you can buy the hardware on ebay (of course much cheaper than the new OS4 solutions)
I cannot say which solution is better because I do not own PPC.
Then Aros: it supports X86, ARM, 68k and PPC and there are solutions that run alone on supported hardware (similar to Linux) or hosted (Linux, Android, Mac and others)
The user generally uses a distribution that includes lots of preinstalled software. For X86 you can choice between Icaros, AspireOS and Broaway X, for ARM (Android) you have now a new distribution and I have created a 68k distribution "Aros Vision". All are free of charge, you can download and test them.
Hope that makes some things clearer.