Easyrtc itself poses no hard limits on the number of users per room.
What you will run into however is bandwidth limits to your outgoing connections (a matter between users and their ISPs) and user's processing power.
You can get around this into three ways
1) set a low camera resolution (320x240) generally works well.
2) use SDP filtering (as demonstrated in the low-bandwidth demo) to reduce the bandwidth allocated to each video stream.
3) Contact Dialogic about using their Powermedia XMS server. We hooked it up to Easyrtc, they are in charge of it's distribution.