I don't like to recommend games without having first played them and properly reviewed their licenses.
However, I have never played an MMORPG and don't intend on playing them all just to make a proper recommendation.
If any of the following do not release full (at least client side) code under a libre license, please inform me so they can be removed.
http://crossfire.real-time.com/
http://ryzom.com/
http://www.worldforge.org/
http://www.planeshift.it/
http://www.mystonline.com/en/
https://www.themanaworld.org/
http://childrenofur.com/
http://www.deliantra.net/
https://stendhalgame.org/
http://www.other-life.com/
http://www.evolonline.org/
http://invertika.org/
https://www.daimonin.org/
http://illarion.org/general/us_startpage.php
http://lipsofsuna.org/
https://www.atrinik.org/
https://www.themanaworld.org/
Again, I have never played an MMORPG so these are not recommendations, just a list of some MMORPG games I found. There are further still many RPG games with online play but not MMO apparently. Sorry for not being very helpful.
I can only emplore other Anons to help you find what you are looking for. Good luck.
Post last edited at