dyne user tools - the /usr filesystem
The /usr directory in dyne contains everything that is not directly needed by the boot and initialization process, therefore anything related to the final user interaction goes in there: applications, documentation and some network services.
The user filesystem is the biggest component of dyne in terms of size, including all the core software: at the current stage of development it weights approx 300MB, including all the graphical X desktop environment, various multimedia and development libraries and more, see SourcePackages for a detailed list of what is included in the dyne:II core.
That of course leave us more than 300MB in a simple CD for inclusion of applications and media.
The dyne.sys file is a compressed (read-only) filesystem that gets mounted in loopback over the /usr, using the squashfs kernel module: 300MB compressed become almost 1GB of space inside the filesystem, which is a lot of space especially if we are going to include new binaries of software.
So here it is the space for customizing dyne, to produce a liveCD based on the dyne system with your own application and media. Have a look at DyneModules if you want to discover how to do that.