If you're asking for a salary for the app up front, the app should be free in the marketplace. You're asking for the community to pay you to produce the app, then asking them to pay again to use it.

I don't find myself agreeing with a lot of directions DP has gone the last few years, this one just seems insulting. You're taking 10 years of work volunteered by other individuals and using that to make a profit for yourself.

Instead of using the app as read-only, make it actually useful and interesting. If you're going to give people access to the DP database, allow them to make updates and corrections straight from their phone. People are complaining about the database inaccurate, you're not thinking of ways to help fix it. Granted, someone will have to verify the changes, but that's why you're making $5 a copy. Justify your paycheck somehow.