The differences between MIT and BSD-3 license seem to be very small and mainly about the 3rd clause of BSD-3 pertaining to the promotion of derived work. Maybe it's still a bit easier for maintainers and users if the license is the same as for Altair, Vega-Lite, and VegaFusion which all use BSD-3. Sphinx uses BSD-2.
I copied over the Altair license and modified the 3rd clause to include the name sphinxext-altair.
The differences between MIT and BSD-3 license seem to be very small and mainly about the 3rd clause of BSD-3 pertaining to the promotion of derived work. Maybe it's still a bit easier for maintainers and users if the license is the same as for Altair, Vega-Lite, and VegaFusion which all use BSD-3. Sphinx uses BSD-2.
I copied over the Altair license and modified the 3rd clause to include the name
sphinxext-altair
.