Is it a free or license
There are two versions of DayPilot for ASP.NET WebForms
DayPilot Lite for ASP.NET WebForms (open-source) https://aspnet.daypilot.org/open-source/
DayPilot Pro for ASP.NET WebForms (commercial) https://aspnet.daypilot.org/try/
See also the feature matrix which compares the feature of both versions: https://aspnet.daypilot.org/feature-matrix/
Is DayPilot Lite for ASP.NET WebForms (open-source) free? https://aspnet.daypilot.org/open-source/
Yes, the open-source version is free.