Completing Racket's re-licensing process

[Sam Tobin-Hochstadt]

With the upcoming Racket 7.5 release, almost all of Racket, including
the core Racket CS binary, the standard library, and the packages
provided with the main distribution, are available under a permissive
license, either the Apache 2.0 License or the MIT License. You can
read the details of the new license here:
https://github.com/racket/racket/blob/master/LICENSE

This has been a long process, beginning in 2017, and we're grateful to all
the contributors to Racket, including those from very long ago, who
gave permission for the re-licensing. More than 350 contributors to
Racket responded; many of the responses can be seen in here:
https://github.com/racket/racket/issues/1570.

More information is available in the post on the Racket blog:
https://blog.racket-lang.org/2019/11/completing-racket-s-relicensing-effort.html

Thanks particularly to Joel Dueck, Sage Gerard, and Pamela Chestek at the SFC.

Sam, for the Racket core team