Documentation
Tutorial
The tutorial introduces the basics and gives examples how to write custom optimization problems and algorithms.
Javadoc
The javadocs contain detailed information about each package, class, and interface.
Technical Paper
The technical paper 
explains the basic
concepts and design decisions that were taken. The bibtex of the
paper is as follows:
@conference{opt4jpaper,
title = {{Opt4J - A Modular Framework for Meta-heuristic Optimization}},
author = {Lukasiewycz,Martin and Gla{\ss},Michael and Reimann,Felix and Teich,J{\"u}rgen},
booktitle = {Proceedings of the Genetic and Evolutionary Computing Conference (GECCO 2011)},
pages = {1723--1730},
address = {Dublin, Ireland},
year = {2011},
date = {July 12--16}
}
Source Code and Change Tracking
All information on how to get the source code is given in the download section.