Wirecast 6.08 to 7.0 Free Upgrade for recent purchasers?

I remember reading somewhere (possibly Facebook, but I can't seem to find the post) that if you bought WC 6 recently then your were entitled to a free upgrade to 7. I bought my copy in last month (May) - what is the cut-off point please, and if I qualify how to I get my free upgrade?

Thanks in advance...