Supported Minecraft Versions:

• 1.8, 1.9, 1.10, 1.11

Requires:

• Skellett
• SkStuff
• SkQuery
• MundoSK
• Skript 2.2+ (preferably Bensku fork)
• SkUtilities

Features:

• Passwords are hashed and salted (a player's plaintext password is never stored)
• Salts are randomly generated and stored for each player
• Utilizes packets to create commands so that login commands are not logged and therefore passwords are not logged
• Stops logged out players from moving without the use of any events
• Very configurable, every message and important option can be changed
• Utilizes pepper
• Logs out a player automatically if their IP changes between logins (on by default)
• You can choose the amount of time as user can be logged out for before they are forced to log in again next time they log in (by default, this is set to 180 seconds)
• You can reset passwords
• Uses UUID to store passwords

Options:

• ipchange
  Valid values: true/false
  Default: true
  Description: If true, players are forced to login if their IP changes between logins
• kickfortries
  Valid values: true/false
  Default: true
  Description: If true, players are kicked after incorrectly entering their password a configurable amount of times
• maxtries
  Valid values: Any integer
  Default: 5
  Description: The amount of incorrect guesses a player gets before being kicked if kickfortries is true
• resetperm
  Valid values: Any text
  Default: reset.password
  Description: The permission needed to use /resetpass
• gravity
  Valid values: true/false
  Default: false
  Description: Whether or not the login armor stand should be affected by gravity
• timeout
  Valid values: Any integer
  Default: 180
  Description: #The time, in seconds, a user has to be logged off before they have to log in again when they rejoin (set to 0 for none)
• list
  Valid values: Any valid list variable name
  Default: logindetails
  Description: The name of the list variable used to store passwords, salts and other data

For other skripters:
Just Ok Login has 4 MundoSK Custom events:

• Login (login)
• Register (register)
• Incorrect password (incorrectpass)
• Kicked for too many tries (incorrectkick)