Ask HN: Would this be legal?

suppose I have a chrome extension that allows anyone to monitor any website for new items, and when a new link appears, it opens a new tab to display the contents of the link. After the extension displays the contents of the link, it sends the html to my app, and my app processes it in some way and sends it back to the user in an email or something.

I imagine a site like Hacker News would have no problem with this. But if you take a site like Craig's List (canonical example) which has a litigious history, I could see them potentially having a problem. However, in this case I am not interacting with Craig's List in any way I am simply doing some processing on some text that is being sent to me.

EDIT: what does craigslist mean by "software expressly licensed by us" does this mean I can send them an email and get them to okay my software if its not something that is competitive with craigslist?