Welcome to the forum, don’t know if I can answer them all.
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There’s even the question if anything can be deleted at all. I heard rumors about the fact that you can delete your data-atlas so you can never get your file back again. But the chunks might live on the network forever. Don’t know where this idea has gone. I would say it is possible. But I think even with you being able to delete it is censorship resistant. Unless under torture or extreme threads where people force you using violence to log in and delete it. Don’t know if that’s what you mean?
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You don’t need to pay coins to run an App. So when you create one, you upload it to the network and you and others can use it. People will run your application local on their machines. So it depends on if they do or not how long your App is used. This is quite different from Ethereum where “contracts” run on the miners computer and nobody can stop the network.
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If think a system where you charge people for using the App should be possible. Although I think people will grab your code and create a free version next to it. Most won’t IMO. Because they understand that it would kill development.
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I think most Apps will be open source. They’re run in a “sandbox” but still people want to be able to read and check the code I think. Don’t know if closed source will be possible.