免费和开源的 Java 虚拟机
AegisVM (inactive since 2004).
Azul Zulu — is an OpenJDK build supported by Azul Systems. It is open source and free to download. The initial release ran on Windows Server 2008 R2 and 2012 on the Windows Azure Cloud. Release in January 21, 2014 supports multiple versions of Linux as well as Amazon Web Services, Rackspace and various hypervisors. Also added an Enterprise version with subscription support available. In June 2014 Mac OS X support was added. 
Bck2Brwsr — small JVM capable to boot fast and run in 100% of modern browsers including those that have no special support for Java. Last release in September, 2013.
CACAO — uses GNU Classpath, supports multiple architectures. GPL. 1.6.0 released September 4, 2012.
GCJ the GCC Java compiler, that compiles either to bytecode or to native machine code. The product is currently in maintenance mode.
HotSpot, the primary reference Java VM implementation.
JamVM — Developed to be an extremely small virtual machine compared to others. Designed to use GNU Classpath. Supports several architectures. GPL.
Jaos — Java on Active Object System. Uses GNU Classpath as a standard library. Unmaintained.
Jato VM — uses GNU Classpath. GPL.
JESSICA (Java-Enabled Single-System-Image Computing Architecture).
JNode — operating system. Version 0.2.8 released on January 29, 2009. LGPL.
JOP — Hardware implementation of the JVM. GPL 3.
JwiK Open Source Java VM for 8bit micro for wireless applications.
JX (operating system) — GPL. Version 0.1.1 released on October 10, 2007.
Kaffe — Uses GNU Classpath. GPL. 1.1.9 released on February 26, 2008.
leDos real-mode x86 JVM running on MS-DOS. MPL.
MateVM — An experimental JIT implemented in Haskell. GPL.
Maxine — meta-circular open source research VM from Oracle Labs.
miniMV (from UABC-Tij for embedded systems and Wireless Sensor network devices).
SableVM — First free software JVM to support . Makes use of GNU Classpath. LGPL. Version 1.13 released on March 30, 2007. and
SuperWaba — Java-like virtual machine for portable devices. GPL. Discontinued, succeeded by TotalCross.
VM02 a Java-compatible environment for the Apple II series of computers.
VMkit of LLVM.
Azul Zing JVM a fully compliant Java Virtual Machine based on HotSpot that uses the Azul C4 (Continuously Concurrent Compacting Collector) garbage collector. Supports memory heaps of 100s of GB without GC pauses and is able to grow and shrink the heap based on load.
CEE-J is a clean room implementation of Sun's Java technology, Skelmir is not a licensee of Oracle.
Excelsior JET is a licensed Java SE implementation with AOT compiler
Hewlett-Packard, Java for HP-UX, OpenVMS, Tru64 and Reliant (Tandem) UNIX platforms
J9 (IBM), for Windows, AIX, Linux (x86 and PPC), MVS, OS/400, Pocket PC, z/OS
"Classic JVM" for IBM OS/400 (superseded by J9)
Imsys AB provides their SNAP (Simple Network Application Platform) JVM running on their proprietary IM1000 and IM3000 microprocessors that feature microcode execution of Java byte codes.
Apogee provides embedded Java using IBM J9 and Apache Harmony Class Library for X86, ARM, MIPS, PowerPC running on Linux, LynxOS, WinCE.
JBed, (Esmertec) is an embedded Java with multimedia capabilities
JBlend, (Aplix) is a Java ME implementation
Mac OS Runtime for Java (MRJ)
MicroJvm (IS2T - Industrial Smart Software Technology) Wide range of virtual machines dedicated to embedded systems (including hard real-time constrained systems), ARM7, ARM9, AVR, AVR32, PPC, MIPS, ...
Microsoft Java Virtual Machine (discontinued in 2001)
OJVM (also known as "JServer") from Oracle Corporation
SAPJVM (SAP) is a licensed and modified SUN JVM ported to all supported platforms of SAP NetWeaver, started as Java 5, in the meantime Java 6 compatible (Windows i386, x64, IA-64; Linux x86, IA-64, PowerPC; AIX PowerPC; HP-UX SPARC IA-64; Solaris SPARC x86-64; i5/OS PowerPC)
Waratek CloudVM for Java A multitenant JVM that allows per-tenant isolation, metering and resource control
C virtual machine (CVM, from Sun), supports C
Gemstone - modified for Java EE features (application DBMS)
HP ChaiVM and MicrochaiVM
Intent (Tao Group)
PreonVM (Virtenio) A VM for embedded systems and small devices.