[randkyp]

It's a trademark thing; there are some prerequisites and manual approval involved before you get to officially name your distro "[Distro Name] Linux".

https://www.linuxfoundation.org/legal/the-linux-mark

[kragen]

that's not much of an excuse for pretending to have written an os; the only real requirement in https://www.linuxfoundation.org/legal/sublicense-agreement is that you acknowledge that linus torvalds owns the linux trademark