What type of software is offered free for trying, with a payment system based on keeping it?

The concept of shareware refers to software that is distributed for free on a trial basis, allowing users to try it before they decide to purchase a license for the full version. Typically, shareware encourages users to evaluate the software, and if they find it useful, they are expected to pay a fee to continue using it or to access additional features. This model enables developers to reach a wider audience by allowing potential customers to experience the software without an upfront commitment.

The other options do not fit this description. Web applications are typically accessed through a web browser without the same trial payment structure as shareware. Vertical-market applications are specialized software designed for a particular industry and may not necessarily follow the shareware model. Software licenses refer to the legal rights granted to use software and do not specifically describe the trial and payment structure inherent in shareware. Thus, shareware is the correct identification of software offered free for a trial period and requiring payment for extended usage.