If he has all the individual records, or can download them all as separate files, Office Word, Excel, or Access should be able to do a "merge" of the individual records into a single database.

The details will depend on the specific form of the records, and on how complete they are, so I won't attempt advice on precisely how to set up the process. Of course if the individual records are on index cards in a file drawer, re-entry of the data may be the best one can do.

A very common error in the industries where I've worked is writing a contract for "development work" that fails to state what belongs to the creator and what becomes (or remains) the sole property of the buyer. A contract or order for the services might help, although it would be unusual for most small businesses (including charities) to be aware of all that should be spelled out. Even an invoice that states what is being delivered and needs to be paid for might help.

In the absence of a very specific prior agreement, a rather disagreeable argument seems likely, regardless of what action is applied. Once there is disagreement, hiring a good lawyer may be the best course of action. (A respectable charity might expect to get a discount(?) if the services required aren't extensive.)

John