That is apparent *nonfree* licence, probably a homebrew one, so it
does not have any name.
Is this a problem?
These icons and few others (which I don't know where they come from) are included in
MultiMC [1] as a theme changeable at runtime under settings. I know about this particular
set because it is included in COPYING.md file.
[1]
https://github.com/MultiMC/MultiMC5/tree/0.6.0/application/resources