Particle Code was acquired a few days back by its competitor, Appcelerator. The acquisition appears to mostly be about picking up the Particle Code engineering talent with their vast experience in making games/applications cross-platform in one pleasant sweep.
However, the Particle SDK beta is coming to an end as a result of being bought out by their competitor. In announcing the acquisition, the Particle Code team mentions, "The Particle platform is and will continue to be completely free to developers, new and old. We may even open source parts of it in the future. Stay tuned."
The Particle Code support team also mentions in their forums, "If we see that many developers are interested in it, there's a good chance we'll open source it."
The Particle Code overview lists the supported target platforms as Apple iOS, Android, Windows Phone 7, HTML5, Adobe Flash, J2SE, BlackBerry, WebOS, J2ME, Symbian, and Windows. Developers can be using a Windows, Mac OS X, or Linux (coming soon) host and be writing their games/applications in Java, ActionScript 3, or C# support is evidently being worked on.
Particle Code works by passing the source-code, assets, and UI layouts to the Particle Engine, which in turn has platform plug-ins and translators. This engine translates the original source and assets into native source-code and components for each targeted platform. This translated-to-native code is then passed to each respective platform's SDK to then produce the native applications and the HTML5 version of the game/app.
The Particle Code platform shares similarities to Google's PlayN project, which is a cross-platform game library that's already free and open-source.