Kaffe, first released in 1996, was the original open-source Java implementation. Initially developed as part of another project, it grew so popular that developers Tim Wilkinson and Peter Mehlitz founded Transvirtual Technologies, Inc. with Kaffe as the company's flagship product. In July 1998, Transvirtual released Kaffe OpenVM under a GNU General Public License. Now it is developed by a world-wide team of programmers. Beside the mailing list, the developers can often be reached via IRC in the #kaffe channel on irc.freenode.net.
Unlike other implementations, in the past Kaffe used GNU Multi-Precision Library (GMP) to support arbitrary precision arithmetics. This feature has been removed from release 1.1.9, causing protests from people that claim they used Kaffe for the sole reason GMP arithmetic being faster than the typical pure java implementation, available in other distributions. The capability was removed to reduce the maintenance work, expecting that interested people will integrate GMP support into GNU Classpath or OpenJDK. Subsequently GNU Classpath introduced GMP support in version 0.98.