You likely misread the sentence. It doesn't say "To learn more, download and install the free browser extension:" - it says, "To learn more, or to download and install the free browser extension:" and then provides you with links to the stores that contain the description for the extension:

> Websites have increasingly begun to rely much more on large third-parties for content delivery. Canceling requests for ads or trackers is usually without issue, however blocking actual content, not unexpectedly, breaks pages. The aim of this add-on is to cut out the middleman by providing lightning speed delivery of local (bundled) files to improve online privacy.

I agree that it's a very weird frontpage and means of describing an extension, but you don't need to run their code before reading what the extension does.