Yes, we will eventually charge for it once we work out some of the kinks in the beta. Our first thought was $10/mo for 100 screens (though I agree with the feedback below, so this will probably go up). Any feedback on that?
An instructive question which was asked to me recently: "Who would be excluded from using this project if it cost [I'll fill in price points: $39 / $99 / $199 etc], is it in their best interests to use this, and do you seek their business?"
Subscriptions work, everyone understands them, there is infrastructure to support them. Just sell them. Do not get cute with your pricing model without a very good reason, backed by data.