The addon can function, again e.g., using the Cyberfox 64-bit version compiled as optimized for Intel processors. Such a configuration has been used for experimental purposes; specifically for testing the addon.
Using Firefox (or browsers based on the Firefox code) allows much customization, including script blocking addons and ad-blocking addons, cache management and cookie management addons, and video addons, (some allowing choice between Adobe Flash or HTML5 for video display), with some download and conversion addons available which allow video downloading at different resolutions as well as audio only stripping. The latter might be useful for long flights with, e.g., even a low-end Windows 8.1 tablet with the VLC media player installed and content loaded to a microSD card.
As with iPhone apps, one must always worry that an addon could contain malware, however, trust and reputation protections exist. If any reader wishes to try the Paywall Pass addon, again, for this wsj.com item, it works.
Is it bad internet etiquette to use such an available product to bypass a content provider's paywall? Yes, but the particular addon is new as of June 10, 2015 (or updated then if published earlier), with, so far, only between 200 and 300 downloads.
While Firefox trails Google Chrome and Microsoft Internet Explorer in browser market share, some people prefer it to the point that it has a larger market share than Apple's Safari browser, or the Opera product, which itself is an excellent product based on Chromium Project code.
While not encouraging or urging any reader to install a product coded to bypass a paywall, which would be improper, it nonetheless is interesting to see cat-and-mouse internet interplay between some large organizations providing content and some users wanting content access on their own terms. As to what may or may not be lawful or unlawful, ask a lawyer. Rules do exist. There can be complications as well as opportunity.
Apart from any specific addon capabilities and complications, alternative browsers to Microsoft's bundled Internet Explorer do exist and using them is entirely lawful if adhering to the rules. Some like Google's Chrome browser, for example, so that it has a very substantial market share.
__________UPDATE__________
For any reader hesitant to install a paywall bypass feature into a working browser, the Paywall Pass developer explains a wholly separate but related browsing process:
The simplest way to do this is to do a search on the name or url of the article and click the first link from a search engine. This has been possible for quite a while, as shown in this lifehacker post from 2010: http://lifehacker.com/5443857/get-free-access-to-pay-walled-content-with-a-simple-google-hack
This addon simplifies that process by simply changing the browser referal field to a search engine and reloading the page elements. It works quickly and consistently; all you have to do is click a button.
[link in original] Knowing that Lifehacker published procedure may prove helpful to users of Chrome or Internet Explorer, or Apple laptops using Safari as the preloaded browser; (users for whom the addon is unavailable). A caveat would be that repeated use of such a paywall bypass browsing method, making it a habit, might arguably breach copyright law; again a point about which only a qualified lawyer might give reliable advice.