This is similar to integrating with a search provider, which all browsers do, for better or for worse. And all search providers are closed source and for-profit: Google, Bing, Yahoo, Yandex, Baidu, etc.
however the precidence of selecting a closed source search provider already exists and is a strong expectation (this was something championed largely by firefox to begin with, as an interesting sidepoint)
There is no expectation of an integrated closed source "cloud reader" and attempts to paint this like "aww gee shucks it would be great it we could do something about this but thats just the way they world is" come off as extremely disingenious, especially as the mobile version of firefox had this feature baked in with no reliance on any third party at all.
