If I decide to stop using the software later, do I keep my website address and my old booking records?

Yes, you keep what is genuinely yours, which normally means your web address, your branding and a copy of your booking history, but the portal software itself is licensed to you rather than sold, so the search and booking engine stops working when the subscription ends.

In practice that means your domain name stays registered in your own name, so you are free to point it at a new site whenever you want. The logo, the text, the photos and any pages you wrote for your portal belong to you as well. Your booking records can usually be exported into a spreadsheet so you have the customer names, travel dates and reference numbers to hand for your own files and for your accountant. What you would not keep is the live portal pages, the connections to suppliers and the automatic voucher and ticket emails, because those are part of the service you were paying for.

Bookings that are already confirmed sit with the airline, the hotel or the supplier, not inside the portal, so where the supplier contract is in your own name those bookings carry on and you deal with the supplier directly for changes and cancellations. Where you were selling through someone else's supplier agreement, the arrangement for existing bookings is set out in that agreement, so it is worth reading that part carefully rather than assuming.

Before you sign anything, ask in writing what notice period applies, what format your booking data can be exported in and who the supplier contracts are held with, so you know exactly where you would stand if you ever move on.