Hello, I have tried out:
AuthDB
AuthMe (reloaded)
CrazyLogin
xAuth
vAuth
LoginSecurity
The only one I could get working for BukkitForge was CrazyLogin it requires (CrazyCore).
EDIT:
Use this:
BukkitForge-1.5.1-283
AuthMe 2.8 (Reloaded)
Note: Inventory clear/protection does not work.
Hope this work, Good luck!