MorphOS has a lot of native programs too and there are developers working on software for it. No it's not an official Amiga branded OS but it feels quite like an Amiga to me; I use the PowerUP version. Never tried OS4 and with all the legal trouble I don't feel like it too at the moment.
And the point that you can buy second hand hardware to run a new OS is quite frankly even crappier talk...
