Adobe, Mozilla - Tamarin

Tamarin is the code name for the AVM2 built for the Mozilla applications. Tamarin will be used as part of the Mozilla project in its future versions of SpiderMonkey, C-based JavaScript engine used in Firefox and other applications that are/will be built using the Mozilla 2 technology.

Basics of AVM2
Adobe's Flash player executes applications written in ActionScript, a programming language that (in its current version, ActionScript 3.0) is based on the ECMAScript language specification and is therefore a sibling to JavaScript. As part of Flash Player 9 Adobe introduced a new virtual machine (AVM2) for executing ActionScript applications; among other things, AVM2 features a Just In Time (JIT) compiler that can convert ActionScript bytecode (the form into which ActionScript is initially compiled) into native machine instructions for much faster execution of ActionScript 3.0 applications.

Tamarin
Tamarin is not an open source version of the Flash player; it is simply the virtual machine embedded within Flash Player 9, and does not include all the other components that make up Flash (including the bits that display graphics and play music and video). Adobe will continue to develop and distribute the Flash player on its own as a product separate from Firefox itself.

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