PaulS:
I don't want to use LiquidCrystal in the sketch program.
You have to. Get over it.
Hiding the use of libraries is not in keeping with open source, so it's not allowed.
I would say that a person is "allowed" to write whatever kind of code he or she wants to.
Hiding code is certainly not in keeping with the concept of "open source" and should be discouraged, but it cannot be disallowed.