The miniscript language itself is MIT License:
https://github.com/JoeStrout/miniscript
The Minimicro code doesn't seem to have any license in the repository or code:
https://www.gnu.org/licenses/license-list.html#Expat
For minimicro-sysdisk: I am suspicious that the author just forgot to include a license. Their other repos are mostly MIT or ‘The Unlicensed (also ‘free’ but not ‘copyleft’), and some have licenses added after creation. Suspicion is not something to be legally relied on of course…