That article speculated that it's a "companion tool for the [Go Programming Language] project".
I couldn't find any other references to iOS apps written using Go, so I'm going to speculate that Ivy itself was written in Go. :-)
https://sourcegraph.com/blog/live/gophercon2015/123653512740
https://sourcegraph.com/blog/live/gophercon2015/123653512740