The comment from the author's original post is quite the non-answer.
"Side note: many people always ask ‘what do you think Apple is going to do about this?’ To be honest, I am shocked that everyone is so shocked by the sheer existence of a 3rd party iMessage client. The internet has always had 3rd party clients! It’s almost like people have forgotten that iChat (the app that iMessage grew out of) was itself a multi-protocol chat app! It supported AIM, Jabber and Google talk. Here’s a blast from the past: https://i.imgur.com/k6rmOgq.png."
"Side note: many people always ask ‘what do you think Apple is going to do about this?’ To be honest, I am shocked that everyone is so shocked by the sheer existence of a 3rd party iMessage client. The internet has always had 3rd party clients! It’s almost like people have forgotten that iChat (the app that iMessage grew out of) was itself a multi-protocol chat app! It supported AIM, Jabber and Google talk. Here’s a blast from the past: https://i.imgur.com/k6rmOgq.png."
https://news.ycombinator.com/item?id=38531759
What did they think was going to happen? Who knows? But I guess they thought it was no big deal.