No, you can't create massively multiplayer online role-playing games (MMORPG) with RPG Builder 3D. The software has been developed by R-GEN Media Software and it is packaged with several tools like: MAP-ED, MOD-ED, SCRIP-ED and PIX-ED. With RPG Builder 3D you can create only small role-playing games. I suggest you contact the developers for further information. Their official email address is
Note: In order to create a MMORPG, I suggest you try utilities like: MMORPG Maker XB or Eclipse Origins - 2D MMORPG Maker.