Okies... right. *Prepares generic MMORPG making answer*
Online gaming is certainly possible in both RMXP and RMVX, but to do it you need to learn scripting at least to a decent level. You need to know what scripts you are editting and why.
There are two routes you could go down really. The first is to use Netplay+. Trouble is, as many have found, it is flawed in some aspects which make it not very newbie-friendly. This is fairly self explanatory, but it's when you get errors or have to make it SDK2 compatable you'll get problems. That's where knowing RGSS comes in. Also you'll need RGSS is you ever come to edit any of the default systems, or add your own systems in.
Netplay+ features trade, chat, guilds, PM'ing, admins and moderators, etc.
The second option is building the system yourself from scratch, which is not all that hard. The basic modules you need are included in the Ruby folder (you just need to copy and paste them into your scripts). These are the TCP module and the Winsock modules (I believe) possible some more. You also need a server, and a Network method to send and recieve data. Now, not many know how to do this, but it should be easy to learn if you know RGSS through just plain simple Ruby TCP tutorials. I know there are some out there as I have seen them. Never actually tried them though, so can't help you there.
In answer to your question, it is possible.
