Sun Microsystems has announced that it is releasing its Java technology as open source under the GNU General Public License version two. Java Platform Standard Edition, Java Micro Edition and Platform Enterprise Edition will fall under the GPSv2 license. The Java Development Kit will also be released as free software.
In the last two years, Sun's CEO Jonathan Schwartz and Chairman Scott McNealy have promised to make most of the company's software available under open-source license which allows programmers to modify and sell code.
Previously Java backend software has only been open to paying customers. Sun's move will put millions of lines of code into the public's hands and the company hopes this will increase its hardware sales.
Java was launched way back in 1995 and promised a write once approach to programming. Java code could conceivably run on multiple platforms without rewrite. While it has certainly become a popular language, Microsoft is pushing its .NET platform heavily.
You can get more details about the platform here.