Add copying file for proper licensure

[ghost]

Stemming from #5, it's now clear the intent of this work is to be free and open source. However, without a LICENSE or COPYING file users running it run the risk of having a renege later. Of course I don't presume anyone would do such a thing—but I prefer not to make assumptions.

As a result, could we please get a copying/license file added to this repository? Note I discourage use of GPL for most works which are not specifically required to be GPL licensed (such as WordPress themes).

In case it's of any help, I've provided some high-level guidance and reasoning on why not GPL here: xwp/wp-dev-lib#240 (comment)

And here are some related resources resulting from license investigation which apply to WordPress libraries and plugins as well as my catalyst for the related investigations—from Jeff Atwood:
https://hackernoon.com/introducing-the-btc-license-28650887eb11
https://github.com/comfusion/hyperdrive/issues/41
https://blog.codinghorror.com/pick-a-license-any-license/

[BFTrick]

Definitely happy to include. Send it in with a pull request please.

[ghost]

@BFTrick Are you good with a BTC license?

[BFTrick]

Since this is an extension of WordPress is automatically follows the GPL license and that's what I'd use.

[ghost]

Oh, you don't want to use GPL for code which doesn't use the WordPress internals. I left some links in the issue description. Specifically check out the following guidance on which license to use and when: xwp/wp-dev-lib#240 (comment)

Note also the only thing WordPress has ever received legal counsel on regarding GPL is themes. Plugins have been sorta lumped in there but AFIAK they were not considered as a part of the ”all themes are GPL“ legal counsel the FSF provided back in '08.