License can be limited on number of CALs. You can manage it on SharePoint Central Administration -> Datapolis Process System -> License Management. There are a few things to remember about CALs:

1. Each user who launches Datapolis Process System Workflow Actions is registered as one CAL and stays in database.
2. Once registered user is not registered again.
3. After the number of used CALs surpasses the limit included in the license no new users can launch Workflow Actions. Users that was registered before can still launch Workflow Actions. Also there is an e-mail sent to farm administrator, informing about the event.
4. Every 24 hours, farm administrator can remove up to two users from the list of registered CALs. The operation can be done on Datapolis License Management page in SharePoint Central Administration. This feature allows you to react to changing organization environment (e.g. when certain users are no longer part of any process).

For remove users from CALs registry please choose (remove users) button on License form.

And then choose CALs to remove using arrows. Finally click on Remove selected users, which will free your CALs registry with that users and allow next users to launch Workflow Actions.