How can I install Cheetah (OSX 10.0) on my 2014 Macbook? Can I use virtual box? Where can I find iso files to install? BTW my macbook is running Yosemite
You will need to virtualize the hardware. PearPC claims to successfully run Mac OS X 10.3, so my best assumption is that it would also run 10.0.
The matter of obtaining and running the OS on your computer is of dubious legal nature, depending on where you live and what licenses you accepted when you purchased and ran the OS.
Any ISO file is likely pirated. Best to buy a CD on the used market or find a local computer group that has a library. If you wanted to be totally legal, buy a used Mac that came with that OS. Replacement media is often available from Apple even long after they stop selling a certain OS.
I can't speak to virtual box other than it's taking more fiddling then I cared to spend. I go with VMWare or Parallels for my virtualization.