Can you outline briefly what the benefit of this is compared to mosh?

Its also Apache 2.0 licensed, compared to the GPL3 that strangles Mosh.

Pity its not a freer license though.

How does a GPL license "strangle" a network connection tool? Are you really bothered that you can't incorporate it into your own BSD/closed source project, or is it a purely ideological "it's not BSD, so it doesn't respect me as a developer" stance?

It's a pain to get mosh support in iOS clients, yeah.

Even with the explicit waiver of anything in the GPLv3 that might possibly conflict with iOS App Store requirements?

https://github.com/mobile-shell/mosh/blob/master/COPYING.iOS

It's a pain to get mosh support in closed-source iOS apps, but I think that's a good thing, and that's more about the closed-source requirement. (Though the iOS requirement means that you can't take the fork-and-exec approach that e.g. JuiceSSH on Android does; your whole app has to be free software.)

There's a free-software one that charges money on the App Store for a precompiled binary, which seems like the right plan: https://github.com/blinksh/blink