Open Source Flash Development
OpenLaszlo is an open-source platform that compiles to Flash 7 .swf files. Development is done through a local web server that is included with the compiler. The applications can be compiled on a production server on the fly, or served as static .swf files. The latter is called "SOLO", and is the way that is useful for chumby developers. See also Developing_with_openlaszlo.
MTASC, SWFMILL & SWFTools
MTASC, the Motion-Twin Action Script Compiler, will compile Actionscript 2.0 files into .swf. A lot of widgets can be created with just this tool. The source to an example Chumby widget developed with MTASC is Star.as.
Swfmill is an xml2swf and swf2xml processor with import functionalities. It's most common use is the generation of asset libraries containing images (PNG and JPEG), fonts (TTF) or other SWF movies for use with MTASC-compiled ActionScript, although swfmill can be used to produce both simple and complex SWF structures.
SWF Tools is a collection of SWF manipulation and creation utilities. These tools can combine SWF files, extract media (GIFs, JPEGs, MP3s. etc.) from existing SWF, convert media into SWF, etc. It also has its own simple language and compiler (swfc) for creating Flash animations. The source to an example widget developed with swfc is star5.sc.
Used in conjunction, these tools provide a moderately-complete, open-source, command-line Flash development environment.
A free, open source alternative to the MX components is SMX, a set of components developed by the BBC and made open source. Lists, Borders, Checkboxes, RadioButtons...
FlashDevelop is an open source ActionScript source editor that can be used with the free MTASC ActionScript compiler.
Please note that FlashDevelop is a .NET application, and as such, is a Microsoft Windows application. As of October 2007, it will not currently compile for Mono, but might run under WINE.
FlashDevelop for Chumbies
Simple Linux Development
If all you want is a simple webcam, and don't want to learn Flash, see Flash_on_Linux_Using_Ming