O’Tierney is less well-known than his co-founders, particularly the company’s CEO Jack Dorsey, but according to his LinkedIn profile (where he describes himself as an iOS engineer), his accomplishments include building the original iPhone app, as well as being a “large contributor” to its first iPad app, the first Pay with Square product, and the Register app.
In a Quora post (answering the question, “Why does Square have so many co-founders?”) O’Tierney writes that he joined with Dorsey and co-founder Jim McKelvey in January 2009. (His prior experience includes working as an iPhone programmer at Tapulous.) Apparently, in those early days the trio worked on Square in Dorsey’s apartment, and Dorsey had to flip up his Murphy bed every morning to make room for his co-founders.
In his tweet, O’Tierney says he’s not sure what’s next, “except for a bit of traveling!” In a tweet directed at The Next Web’s Jon Russell, he added, “I left on good terms. I just want to do something different. Square’s still in a lot of brilliant hands!”
I’ve emailed O’Tierney and Square for comment, and I’ll update this post if I hear back.
Update: Square declined to comment.