ChessBot is a free UCI chess engine written in Java. It is not a complete chess program and requires some UCI-compatible GUI (e.g. XBoard with PolyGlot, eboard, Arena, Sigma Chess, Shredder, Chess Partner or Fritz) in order to be used comfortably. Read the documentation for your GUI of choice for information about how to use ChessBot with it.
Install the latest (>= Java 1.8) Java Runtime Environment from https://java.com/en/download/, or install the Open JDK (sudo apt-get install openjdk-8-jre)
To execute ChessBot as an UCI-Engine run java -jar ./ChessBot.jar.
To use ChessBot with hash table you may need to expand the default heap size uf the java virutal machine. Build hash table with java -Xms4096M -Xmx614 -cp bin search.hashtables.MainTranspositionTable.
To execute ChessBot with hash table run java -jar -Xms4096M -Xmx6144M ~/ChessBot/ChessBotBBHash.jar
ChessBot is free, and distributed under the GNU General Public License (GPL). Essentially, this means that you are free to do almost exactly what you want with the program, including distributing it among your friends, making it available for download from your web site, selling it (either by itself or as part of some bigger software package), or using it as the starting point for a software project of your own.
The only real limitation is that whenever you distribute ChessBot in some way, you must always include the full source code, or a pointer to where the source code can be found. If you make any changes to the source code, these changes must also be made available under the GPL.
For full details, read the copy of the GPL found in the file named LICENSE