Jazz Jackrabbit 2 Plus (JJ2+) adds countless features and bug fixes to both Single Player and Multiplayer gameplay within JJ2, and is used almost universally by most serious players. It has much better network code than the original game, adding console commands to online games, fixing most major game-crashing errors and connection problems, allowing permitted clients to log in as "remote administrators" in someone else's server and control the gameplay, and adding several new multiplayer gamemodes. It additionally fixes or enhances many of the events in the game, and allows level designers far more power than in regular JJ2 through the addition of an easy-to-use scripting language. JJ2+ takes everything great about JJ2 and adds so much more on top of it; it is truly a must-download. JJ2+ is distributed under the MIT license.
This screencap highlights many of JJ2+'s most useful features. The game's dropdown menus have been greatly expanded, stretching far beyond the old simple Pause and Exit buttons and adding numerous options for beginning and ending games, setting weapon parameters, adding time limits, and so on. The bottom left shows the Chatlogger, a new window added in JJ2+ that records all discussion and notifications in online games and may save the log to the harddrive at any time, which is vitally useful in online tournaments. On the left is a section of AngelScript used to change the water color in the pictured level to make it more lava-looking, an action completely impossible prior to JJ2+.