I emailed rms about this question in 2018. Here's his response: The term "MIT license" is a confusion. It is used to describe two different licenses;

I emailed rms about this question in 2018. Here's his response: The term "MIT license" is a confusion. It is used to describe two different licenses; see https://gnu.org/licenses/license-list.html. We call them the X11 license and the Expat license. To distinguish them, we do not use the term "MIT license". The X11 license was, as far as I know, first used by X11. I don't know how it was written -- the question is not interesting to me. After emailing a few other people I got a response from Hal Abelson. Hal's recollection is that it was written by Karen Hershey in the Technology Licensing Office. Hal said that him and Gerald Sussman asked that the license be written for Scheme. Karen Hershey is perhaps a misremembering of or married name of the Karen Keefe in the document's figure 1.