This is not โnecessaryโ, but piracy is a big problem, and if I were you, I would use a licensing library. FWIK does not require the user to always be online, so he is not as intrusive as you think.
People are weird - they donโt think twice about buying a cup of coffee for $ 4 every day, but if they have the ability to illegally download a pirated copy of the application for $ 0.99, they will most likely do it instead from shelling and developer support.
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