Now this is where the public data gets confusing. If I use open maps API and build my database, how can it be proved that via which API (Google Maps or Open Maps) it has been built to be accused?
That will probably come down to how well your defense is against Google's lawyers.
Now, I'm not a lawyer but I have read and been involved in my fair share of contracts. My understanding is that you might not be able to claim negligence that you were unaware or you were not sure. They might ask you to take down the entire database if you have not proof which data is from which API.
Now this is where the public data gets confusing. If I use open maps API and build my database, how can it be proved that via which API (Google Maps or Open Maps) it has been built to be accused?