A trial version is attached to a given account, based on the person's e-address. If your client purchases a license within the designated timeframe after his trial period ends, everything in his Articulate dashboard will be kept in his account. (Check the sales/pricing info for details about how long Articulate keeps Rise and Review content created during a trial.)
- If you're actually the one using his account, you'd still have access to those materials.
If you purchase a license with your e-address, you won't see anything from your client's account. However, he can send you a copy of any Rise courses.