add non commercial license

[hejazizo]

No description provided.

[CLAassistant]

All committers have signed the CLA.

[arf1372]

I see you added a CLA checker bot. Would you insert appropriate instructions on this to CONTRIBUTING.md?

I want to mention this license (CC-BY-NC-SA 4) prevents ANY commercial reuse of this material for ANYONE EXCEPT OWNER. If you mind allow some "fair commercial usage policy", please add it to README file.
You also would prefer a "dual-licensing scheme" for these situations.

Also, ensure materials used in this repo allow application of a NC (or even a CC) license at all! Attributions and citations must be clear and right. Can you - at least - refer to an attribution list to check compatibility and to avoid copyright infringements/plagiarism?

P.S: I do these precise considerations because: 1st. CC licenses are Irrevocable. 2nd. Once this branch merges and the work publishes, the license applies to this and all foregoing works as long as these license terms reside here.

[arf1372]

Regarding to attribution/citation part here:

Also, ensure materials used in this repo allow application of a NC (or even a CC) license at all! Attributions and citations must be clear and right. Can you - at least - refer to an attribution list to check compatibility and to avoid copyright infringements/plagiarism?

This means every single material come from any outside source must have clear and correct citation and bibliography on each file.

[arf1372]

@hejazizo As this repo now has an Expat license (MIT), would you mind closing this PR?