Would like to fix the license shield as well, but unsure how to tackle yet.

GitHub's parsed metadata reports unknown license: https://api.github.com/repos/bats-core/bats-core

Github is supposed to use licensee gem, which sorta identifies the right license:

$ licensee 
License:        NOASSERTION
Matched files:  LICENSE.md, package.json
LICENSE.md:
  Content hash:  b3c0fbcf548230f1eeeabfecbb199b06be37e1e0
  License:       NOASSERTION
  Closest licenses:
    MIT similarity:      87.08%
    BSL-1.0 similarity:  64.63%
    UPL-1.0 similarity:  61.89%
package.json:
  Confidence:  90.00%
  Matcher:     Licensee::Matchers::NpmBower
  License:     MIT

Did a little searching and apparently a lot of other repos have had the same issue (licenses no longer correctly being identified by github). So presumably the licensee gem report doesn't really matter.