I was going to make a joke about beta selections being made based on donations of Starbucks in my direction, but I'd probably get fired...
To start, we'll literally hand pick some users based on internal criteria; it *might* literally be the immediate friends and family of staff and gamedevs, but it's still undecided. I'll be building out the beta user scheme myself this week.
From there, the beta.armorgames.com page will have a sign-up form for you to give us your Email address. When we're ready to take on more users, we'll send an Email to a batch of users. And, as I mentioned, we've also looked at letting users invite a couple of friends, but that's not confirmed yet.
That's all I can share at this time.