You can use BigBlueBUtton software. It is a free and opensource web conferencing software. there is no limit to share the number of webcams in a session.
OpenMeetings is the another opensource, web-based software. It provides screen sharing facility as well. It has been downloaded over 250,000 times.
Mconf is an open-source and free web conferencing system....
Not a true RDP program, but since you're using Windows, you may want to look into the Microsoft Garage project called "Mouse without Borders". This allows you to control up to four computers on a network with a single mouse and keyboard; you can also copy and paste data between them.