Even though you do not plan to distribute a runtime, do you have FileMaker Advanced? It has an option for removing the admin account that would be a useful part of protecting your file.
If selling online, without direct contact with your customer, a demo runtime is useful depending on the database.
It is easier to protect the application than distributing the database to FMP users.
A Paypal account, and an online selling agent such as esellerate makes the distribution more transparent.
I was fond of esellerate before it was purchased by Digital River. I am investicating Oronjo, among others.
Note: it is free and focused on low cost ($1) or free content.
A FMP Developer documents his process...
All Encompassing Question (and Answers) on Copy Protection and More
FROM Shrink Wrap Solution Developers
Discussions for developers producing and distributing shrink wrap solutions.
Hi, PMJ Yes I am using Filemaker Advanced 11 and 12