There is plenty of sites offering database searches and I wonder how to make it without breaking any laws. I'm looking for games source (pgn ideal) that I can download, process and use in my application. Looking for both human and correspondence sources. No big problem if the work is heavy or difficult. Interested just in new games so if some sources started just a few years ago, no big deal. How complete various sources are? Can I just pack the database to my own format and offer it as a free download?
Nobody has copyright to raw PGN games, so you are free to distribute it. You may pack it to your own format, you may offer it as a free download, or you may sell it.
However, you can't sell annotation. You may use Chessbase's
2017 Mega Database, get the games, remove annotation (if any) and use the games for your app.