@drewdevault@fosstodon.org This *is* allowed as long as it's clearly understood and documented that, while their source is MIT licensed, the resulting *binaries* are covered by GPL.
I've done this myself (writing permissively licensed code calling a copyleft library, creating copyleft binaries) so that my source remains permissive and can be refactored or adapted for use with different libraries (allowing creation of a non-copyleft binary from it in the future).
For example, writing BSD-licensed unit tests for a BSD-licensed library that also calls FFTW (GPL) to create stimuli for the tests.
I want it to be possible to rewrite these tests for use with a different FFT library in the future if needed, producing a fully non-copyleft test case.