Library database for smaller company

Hi!

I am currently working for a small community of researchers and
archaeologists, (see no budget) and my role is to update and
modernize their database. Currently they are using a cal file to very
sporadically add stuff, and they have very clearly hit a limit for
what this poor document can do for them.

As a result I am looking for cheap, preferably free
database solutions dedicated to libraries, currently exploring Koha
to see if fits, but I would be super grateful for any suggestions.