From: Craig on
Haven't used this but it's cross-platform & F/OSS

> SWFTools is a collection of utilities for working with Adobe Flash
> files (SWF files). The tool collection includes programs for reading
> SWF files, combining them, and creating them from other content (like
> images, sound files, videos or sourcecode). SWFTools is released
> under the GPL.

>
> SWFTools has been reported to work on Solaris, Linux (both 32 as well
> as 64 bit), FreeBSD, OpenBSD, HP-UX, Solaris, MacOS X and Windows
> 98/ME/2000/XP/Vista.

<http://www.swftools.org/>

--
-Craig