An open source implementation of the GameOfGo. Apparently version 3.2 is about 10 kyu in strength.  Version 3.6 is the current version (slightly slower but stronger).

The main page is http://www.gnu.org/software/gnugo/gnugo.html

The development page is http://www.gnu.org/software/gnugo/devel.html

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The GnuGo project uses TestDrivenDevelopment to a great extent.  There are several types of automated test suites used for RegressionTesting, comprising life-and-death problems, common shapes, joseki (openings), and mistakes from GnuGo's own games.  Typically, tests are added which GnuGo fails, then someone tweaks the pattern database or code to pass those tests, while on the other hand neither breaking the other RegressionTests nor exploding the search node counts.

When the developers run out of elbow room for more improvements, they can confidently work on optimization and refactoring [WhatIsRefactoring] knowing they can run the RegressionTests both to measure improvement and guard against introducing bugs.

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See GoOnLinux, GameOfGo, ArtificialIntelligence