The bottom line:
1. You can extract it with Universal Extractor, but it's a bit of a mess
2. The installer can make a portable install, but still saves the install path to the registry
3. The included xulrunner means you don't have to copy Firefox (though it does write inconsequential settings to %APPDATA%)
4. You could just put a relative path to FirefoxPortable.exe as your browser path
5. The latest build runs the setup wizard in your default browser every time you start MediaCoder (despite checking the box not to do so)
6. The installer includes OpenCandy, which will cause those very concerned about privacy to balk.
You can use Universal Extractor, but the folder structure is confusing when compared to my portable install (for which I used the installer under Sandboxie and copied to its current location). The files and folders in the "$31" directory seem to get sprinkled in a number of subdirectories. There's no "xulrunner" folder or "xulrunner.exe" anywhere in the extracted files, though these exist in my portable install.
The installer now includes a "save data files in program folder" option, which makes a portable install, but it still saves the install path to the registry.
In light of the above two complications, I'd recommend either doing an install - copy - uninstall or using Sandboxie. An additional advantage to using Sandboxie is that the OpenCandy data will not be stored on your computer.
There seems to be a bug in this build: I can't avoid it running the setup wizard in my default browser (I switched the default to IE to make sure it wasn't just running Firefox) every time I start it, even though I've checked the "Do not show this page on next startup" (and I even went through the whole wizard just to see if that would help).
After struggling with it for way to long, turning to Google and the Mozilla Knowledge Base for help, I'm pretty sure that xulrunner cannot be made to run "stealthily". However, there's no reason to change the settings for the included xulrunner (stored in %APPDATA%\Broad Intelligence\MediaCoder) anyway - they're inconsequential to the operation of MediaCoder. So it would seem that MediaCoder is portable with the included xulrunner (no need to copy a Firefox install), but it's not stealth. However, if you're running FirefoxPortable, you can just use a relative path to FirefoxPortable.exe in the settings (which can be accessed in MediaCoder under the "file" menu, or by manually editing prefs.xml).
Finally, some might consider OpenCandy to be spyware:
Code:
http://www.opencandy.com/what/
http://www.opencandy.com/blog/entry.php?id=4