I've tried to find some chess engine source which would be completely free for any use. But most of open source engines is under GPL license. At least LGPL would be nice. Ideally I would like some version which I could change and then use in my non-opensource program. Do you know any?


The main difference between the GPL and the LGPL is that the latter allows the work to be linked with (in the case of a library, 'used by') a non-(L)GPLed program, regardless of whether it is free software or proprietary software. The non-(L)GPLed program can then be distributed under any terms if it is not a derivative work. If it is a derivative work, then the program's terms must allow for "modification for the customer's own use and reverse engineering for debugging such modifications." Whether a work that uses an LGPL program is a derivative work or not is a legal issue.


3 Answers 3


I've been looking for the same here. I haven't found a LGPL chess engine in C++ / C#, but if you can accept Java as the programming language, you can take a look at FluxChess http://fluxchess.com/flux/


There are a lot of chess engines written in C#. Unfortunately, 99% of them use the GPL.

All except this one. It uses the LGPL, but unfortunately, its very early in development, so you might have to choose using the GPL, or using a very early engine.

  • 1
    One way to deal with a GPL library is to write a program, accessible via some sort of RPC mechanism, that provides the library as a service. You'd have to GPL the service program, but then your actual program can be closed-source, since it doesn't link against the GPL library. This is usually more trouble than it's worth, but if one gets really stuck, it's a possible solution. Jul 21, 2015 at 19:31

Did you check on sourceforge.net ?

I see:

  • 5 public domain
  • 1 creative commons attribution
  • 6 BSD
  • 3 LGPL
  • 2 MIT
  • plus 2 Eclipse + 1 Mozilla, although I am unsure of what those licensees imply.

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