License for Slime

Dear Slime maintainers,

I would like to contribute some code to the project, but my employer
(Google) will only permit you to do so if the project is licensed under an
OSI-approved license (https://opensource.org/licenses). I'm not a lawyer,
but my understanding is that "public domain" code is more complex legally
than code released under one of the OSI licenses.

Would the authors consider adding such a license to the project in a
LICENSE file?

Best,
Red