GNUBridge is a Contract Bridge program written in Java and available under GNU public license v. 3.
Note, there haven't been any updates to this project for awhile.
##Users: Download from homepage: gnubridge.org
##Developers Need a minimum of Java 1.5. Builds with Gradle wrapper (ie: %./gradlew build). Need at least 1Gb to run (more is better), so in IDE you need to pass a VM option -Xms1024M. This is already configured for gradle wrapper.