to me that's a hard question, but I'm afraid there might not be a much better answer:
How different is the database from adempiere?
metasfresh and ADempiere have a common ancestor (i.e. ADempiere as it was aprox ten years ago) and you would recognise many things, like
IsActive etc columns in most tables (you guys still have them too, right?).
Also we still have a lot of common table names like
C_BPartner etc. with many common columns like
For instance could I run a migration script on the adempiere seed DB?
I'm pretty sure that won't work.
what would a migration from Adempiere to MF entail?
I think migrating from ADempiere would be easier than your average migration to metasfresh, but it's still a "real" migration project.
So in other words, I would not even try to apply the metasfresh SQL scripts to ADempiere, but rather take a vanilla metasfresh and import the data from ADempiere, using metasfresh import features where possible and direct SQL where needed.