Clarify the license status

[grahamc]

I just noticed nixos-org-configurations has no license. Shouldn't be too tricky, but we should find everyone who contributed to the status page and get a +1 on making this repo MIT or something.

[grahamc]

fwiw I'm in favor of making the code I wrote for this repo MIT, though ideally the commit introducing it would be "authored by" me.