Following through on a promise made last September, Oracle will now offer its legacy JRockit Java Virtual Machine (JVM) at no cost for personal and internal use.

The company, however, will not release the underlying JRockit code as open source, according to a blog post announcing the release and written by Henrik Ståhl, JRockit program manager.

This move to free the enterprise Java runtime software is part of a larger plan to unify the plethora of JVMs that Oracle now possesses, thanks to its 2010 acquisition of Sun Microsystems and its 2008 acquisition of BEA Systems.

BEA Systems originally created the JRockit JVM, which Oracle later folded into its own Fusion middleware stack. JRockit features a number of enterprise-friendly features, such as an advanced management console and a robust set of diagnostic tools.

During last year's JavaOne conference, Oracle announced it had started merging the best bits from JRockit with Sun's own JVM, and releasing the code in a combined open source JVM within the OpenJDK package. Oracle is also merging elements of its legacy Java standard edition JVM, named HotSpot, into the OpenJDK as well.

The JRockit software is now available at no cost for personal use, as well as for internal organisational use. A new licence, which is a slightly modified version of the Sun Binary Code Licence, describes the terms of use. JRockit can be downloaded from the Oracle Technology Network.

The low latency real-time edition of JRockit will not be part of the free package, though the company will still offer this version commercially.