The downloadable copy of CouchCMS is time-limited ( 30 Days) but is otherwise fully functional.
It is meant simply to be tested on your own setup. After the set time expires, yes the script will cease to work and ask for a license.
We provide free licenses for personal and non-commercial sites. If your site happens to be one of these, please contact us with the domain name and we'll send you an unlimited license.
If the site is a commercial one, you'll have to buy a commercial license.
Once you place the new license in your Couch folder, the script will resume functioning without you losing any existing configuration or data.
Hope that answers the question.