"Free, provided by First Church"
The organization or Original that hosts the twin covers each session with one of their own Studio Credits. You pay nothing; you just need an account. Common for churches, schools and ministries that want their twin available to every member.
"4 credits per session"
The owner has set a price in credits (minimum 2). The price is shown before you start, and the credits come from your balance when the session starts. The Original earns a share of every paid session. Common for authors, coaches and experts.
What if a free twin says sessions are paused?
The organization's monthly Studio Credits have run out. The twin's owner can add credits, wait for their Studio Credits to refill next month, or switch to a small per-session price that you would cover from your own credits.
Why would I pay for a twin when general AI is free?
You are not paying for an answer. You are paying to reach one specific person's point of view, drawn from their own work, from someone you already trust, with that person behind it. The twin is a front door to the person, not a substitute for them.