The free version of ChronoForms is fully functional except that it adds a "Powered by ChronoForms" strap-line under each form and email and shows you a pink reminder message in the Forms Manager.
Latest versions will also have a few advanced features disabled on the frontend of the form if you have the free version.
Here is how a contact form will look like on the frontend if you have the Free version:
But on the admin side everything will be working:
You can see the current subscription prices on the Shop page. Subscriptions are not recurring.
A subscription entitles you to a number of 'validation keys'. Each validation key can be used on a single site (note that sub-domains are included).
After purchase you can validate your domains on the My Validations page
If you buy a subscription and validate a site then, on that site, the strap-line is removed and the pink message is replaced by a green one.