I've just got back from vacation and finished the billing system I was working on before I left. Along with it, I improved many parts of the system and fixed known bugs.
I shipped this version, and now Backup Fire is a paid product. It's still cheap, starting at $9/month when paid annually. I'm going to increase the price when I add more features and make the product more overall polished. But, for now, I want to let early adopters enjoy a discounted rate as a symbol of gratitude for trust and support.