Yes to the first question, it generates platform-specific build files (e.g. Makefiles for Unix/Linux), which don't need cmake itself to build the software. Regarding the second question, I believe so, but I'm not sure.

Of course once the makefile is generated, there is no need to use cmake (as long as the project is not modified), but you cannot share a makefile generated by cmake, not even redistribute it. You cannot even re/locate it on your hard drive.

The difference is that autotools generates source distributions that do not need autotools to build, while a cmake project always requires cmake when building.

Oh, I wasn't aware it wasn't distributable, my bad.

Can we give everyone exactly the same tarball of a project and just have it unpack and build on their platform?

I think so, if you pre-generate the build files for every platform and distribute them all in the tarball.

Haha