Can I Use Ground2Cloud for Custom Elements?

If the product communicates using HTTP over TCP/IP, it should work just fine.  This assumes that the element was built to be used on-premise or that the on-premise communication protocol is the same as the hosted protocol. If it’s not, you would need to create a new “on-prem” element, but if so then you should be able to hook it up pretty easily by just adding a new service connection on g2c: