shareware 
Copyrighted software that is available on a free trial basis. After the trial period, users are expected to register the program and pay a fee to the developer. To enforce this, some programs are partially disabled, stop working after a set period of time, or contain "nag screens" that pop up frequently to encourage users to register. Registered users get a full-featured version of the program, documentation, or free updates. Shareware is available from several sources, including Web sites, centralized archives on the Internet, and local bulletin board systems. Shareware that doesn't involve a fee is called freeware. Software that is free of copyright, as well as free to users, is called public domain software.