There's nothing stopping you from downloading the .psarc files, whether you have the game or not.
There is the WIP charter Shroud posted, but there is also "Charter" which is also being developed. You can find it on GitHub here.
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That being said, you can still purchase the physical copy of the game and redeem the Steam code, which lets you download and play it like normal. So saying it's not available isn't entirely true.
There are at least 3 different copies available on Amazon (1 - 2 - 3). They aren't cheap, but it's the price you pay for a delisted game with very limited physical copies left.