Good luck finding the legal contact, not to mention suing, some random developer in India who apparently already abandoned the project.
I will also point out that if you fail2ban the IPs requesting the spamblock list, it could become worse if the browser just retries endlessly in the background. The traffic for a 404 page could be much smaller than the traffic of the very same devices trying again every few seconds, constantly, instead of only checking that 404 every app restart.
In general, the client socket needs to timeout on black-holed connection attempts (several minutes), and the server never sees a TCP handshake packet if the IP is on the global routers ban lists.
As a side note, some people build spider traps that reply with a pre-baked bzip file as a spoofed HTML compressed response. Thus a client program dutifully decompresses a few TB sized document, and browser exits due to memory issues. Note most modern Browsers are wise to this trick these days, but I doubt a dodgy plugin disk-usage limit check would catch a client side storage-flood. People shouldn't do this though, even if it is epically funny and harmless. =)
The client can just set a custom timeout and close the socket after 5 seconds of no or low activity. Then try again.
On your side note; EasyList probably does not want people to start suing for starting to distribute malicious content to users (and crashing your browser on purpose is arguably malicious).
There are all sorts of games people could play, as a DoS is technically an act of war under some legal systems. For example:
1. take the top 200 most popular websites in the given nuisance area
2. add ban rules to a version-B list that also includes all social media, search engines, and Wikipedia.
3. Look at the user-agent string for that specific problem client, or extreme apikey quota abuse
4. Randomly serve version-B filter list that breaks the browsing experience after a frequent update. Increase random breakage until traffic rolls off to normal levels.
The TOS for the ban list file does not specify which sites it will ban, and most users will just assume it is the App that is broken (it is already). People should not do this either, even if it is also funny and relatively harmless. Also, suing people while participating in an attempted crime probably would not go well. =)
Even then I would not do this without clearing it with a lawyer first. You could still end up at the wrong end of a lawsuit that you'll have to defend in India.
There are numerous legal/accounting specialists that protect businesses and investment decisions. We already won't serve _any_ content to IN networks as business policy... so are unlikely to ever have to visit with the cobras.
I will also point out that if you fail2ban the IPs requesting the spamblock list, it could become worse if the browser just retries endlessly in the background. The traffic for a 404 page could be much smaller than the traffic of the very same devices trying again every few seconds, constantly, instead of only checking that 404 every app restart.