It appears the extension would like to read and change the data on any website I visit. I assume users are the product here, so this appears somewhat sketchy since I'm not sure what personal data of mine is being sold.

Perfectly reasonable response, but we are actually not doing anything with individual user data, and we have no plans to do so. We don't even have any plans to do anything with aggregate user data, though we might eventually do that.

The reason that permissions are needed is that the extension monitors how long you read on each website. But that data never leaves your computer — it's just used to compute the stats we show you in your dashboard.

Read Across The Aisle is related to my main startup, BeeLine Reader, and it was just something we did for fun, and to help with polarization of news consumption.

This is great news, I was just thinking that I was annoyed at their paywall... What's the catch?

There is literally no catch. I just launched this as an offshoot from my main startup, and I have no plans for direct monetizing of Read Across The Aisle. The only way that I benefit is that this app raises awareness for my other startup.

See my response to a sister comment for more details!

But why would the WSJ consent to this? I find it exceedingly hard to believe that they don't get anything in return.

Branding, I think? They also get access to our across-the-aisle user base, so it's possible they're not losing too much revenue with the partnership.

To be honest, I've been surprised at the interest this project had received from major media companies. We actually were almost acquired by a large media company that wanted to build a new brand and put Read Across The Aisle as a central part of it.