GNU GPL license question
<p>Lets say I design an entertainment app and when I finish the app I realize that there is a lot of fowl language and want to use a GNU library for something like checking for curse words. </p>

<p>Would using a library as such be a problem legally for selling my product later? (or having it as a closed source project)</p>

<p>Yes and no.</p>

<p>There's two situations to this.</p>

<h3>You own all the copyright:</h3>

<p>If you own all the copyright, then you're clear. you can license your software under the GPL, sell it, and bring it back to a closed source application later on. There's one detail: If someone has an open source copy of your software, they are entitled to use it subject to terms of the GPL. You can't take back their license.</p>

<h3>You do not own all the copyright:</h3>

<p>You can sell the product, however, everything has to be under the GPL, and you can't bring it closed source afterwards, especially if you continue to sell it. This is because through selling it, you convey a form of the software, and an offer of source code must accompany it.</p>

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