Sun Microsystems plans to release the first Java code later today under the General Public Licence (GPL). 

The vendor will release the source code for Java C and Hotspot VM, as promised in August, both of which are components of the Java Developer Kit. 

Sun will also unveil a Java help system, and a release of the Java Virtual Machine is promised for early 2007.

The company said at JavaOne in May that it would release Java under an open source licence, but did not disclose which licence would govern the application.

Sun is also adding the licence to its enterprise grade Java EE. Until today the code was available only under the open source Common Development and Distribution Licence.

Picking the GPL will allow Java to expand its reach in markets such as emerging economies and education, according to the vendor.

"One of the key objectives is helping to drive more volume and adoption for the Java platform," said Rich Sands, community marketing manager for the Java SE platform at Sun.

"The GPL is a particularly good choice to help Java get into some markets where adoption is not as good as it could be."

Sands added that it is too early to say whether Sun will switch to the forthcoming GPL version 3 when it comes out next year.

Sun's choosing the GPL will make open source Java less attractive to commercial vendors that want to use the code as part of proprietary software.

IBM, for instance, could mix the code with its WebSphere Real Time Java SE implementation, but would then be required to disclose any changes to the code. 

In addition to releasing the open source applications, Sun will keep issuing commercial Java licences that allow vendors to create closed source Java certified application servers.

Vendors could contribute code to Sun's open source Java implementations, retaining the copyright for their contributions but authorising Sun to use the intellectual property as well as grant a patent licence.