[unclebucknasty]

>How is this legal in any shape or form?

IANAL, but have some experience with this from a business matter, resulting in obtaining advice of counsel.

And, yeah this is not a criminal matter, but a civil one, so you're right that the developer isn't likely in civil breach unless they are using FB resources (e.g. API or SDK) that they access under agreement with FB and are violating.

The irony is that if the FB standard user agreement prevents users from, say, using software to programmatically access the site, then it's the user of the extension who would be in breach with FB.

So, as long as the developer doesn't use the extension on their own FB account, then FB doesn't have much to stand on (and even then the C&D would only be applicable to the developer's use of the extension as a user).

On a related side note, if the extension actually did something not related to a specific account (e.g. scraped a public profile while not signed in), then even the user would likely not be in breach, as there is no affirmative assent (i.e. clickwrap) to terms of use required to simply visit the site.

[invokestatic]

There’s actually a concept of tortious interference, which can make you liable for assisting other people in breaking a terms of service, even if you never broke it yourself.

[unclebucknasty]

Yeah, I'm familiar with that concept too and actually nearly filed an action against a competitor for it (wish I had, as it was clear cut).

But, my understanding of the standard for that particular tort would make it difficult for FB to prevail. In particular, the two tests that might be hardest to meet are that FB would have to show damages and they would have to show that the developer's conduct led to the breach.

I'm not sure that merely creating a tool qualifies, especially for the latter. The user is not coerced or compelled by the developer to violate his agreement with FB.

Again, IANAL. Just thinking back to legal counsel I've received (and quite possibly misapplied here). Definitely plenty of gray area in civil law.

EDIT: Thinking back to this specific extension, it may be even harder for FB to prevail on tortious interference. The tool merely automates actions that FB makes freely available to its users. And to some extent all access to a site is "programmatic". So, I wonder how this compares to ad blockers or even other built-in browser capabilities that could "programmatically" alter the user experience when accessing FB's site. Really interesting.

[zja]

Sounds similar to what happened when Blizzard sued a company for selling World of Warcraft hacks. https://en.wikipedia.org/wiki/Glider_(bot)

[invokestatic]

Funny you should mention. I only know this cuz I used to sell cheats for games.

[bryanrasmussen]

I would suppose for any extension to work with Facebook the site it would need to be developed with knowledge of a Facebook page's DOM, as such the developer would need to go look at the page to be used and write code to do what the extension needs to do.

Thus I guess one legal argument would be that the ability of the extension to work proves the developer's use of Facebook the service even though they have been banned. So maybe there is something from that they can build up an argument, although it starts to sound far-fetched enough I might expect a judge to not buy it.

[polynomial]

Browser extensions don't kill FB accounts. People kill FB accounts.