The code used for the effects is based on the effects added by the EffectLib Bukkit plugin, made by elMakers and Slikey.
It has however been changed both to be compatible with the mod loader and to add functionalities.
You can find a copy of the LICENSE for EffectLib in the el_LICENSE file.
You can find the source code of the EffectLib project on https://github.com/elBukkit/EffectLib