amvCalendar comes with completely open source code and customizable forms. You will receive an .accdb database, whose elements you can easily import into your own database.
Sharing it with your users or clients is not a problem. There are no DLLs or other files that you need to install – amvCalendar uses 100% Access objects and VBA code.
There are no limits to customization for your application, as you can completely modify all elements, both code and design.