In case you didn't get the email, iShowU, iShowU HD/HD Pro and Stomp are being end-of-lifed sometime in 2017.
Short version: the old apps are being retired. Here's a copy of the official announcement:
Looking back over the old ‘family' album, iShowU was born in 2006 and it developed quickly over the next year. After that came Stomp and then iShowU HD. These were my first “real” products on the Mac. It was an amazing time.
It’s now 2017 and in computer years, that’s ancient. They’re now like some of our dear grandparents: showing some weird quirks (when on modern mac’s), and becoming increasingly difficult to keep up to date. They’re all built on old tech, old API’s … many of which have been deprecated since … oh, about OS X 10.7 actually. So I’ve made the difficult decision to find a retirement village for iShowU, iShowU HD/HD Pro and also Stomp.
They’ll be moving out of home (the store) over the next couple of months, and then I’ll refurbish the storefront, adjust support articles and the like. So I just wanted to give you a heads up that this will be happening very soon!