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Also, why is this on a .org domain?

It's an open source project - the source is available here https://github.com/wallabag/wallabag

Ok, I stand corrected. But to be honest, the webpage looks so much like it's a business that I can't blame myself for being fooled here ...

It's the Wordpress model. Host wallabag.org yourself, or pay for the hosted service wallabag.it.