Like so many other Dreambox tasks this sounds easy at first, but can get quite complex
First you need to have a PC that is broadband connected or better. The build will download a LOT of stuff from the internet as it goes.
Second you will need to get the source. This is covered in detail here http://cvs.tuxbox.org/. Click on the installation instruction link and CHECK each of the prerequisites are installed and active on your box. This is crucial to getting a good build. I use Mandrake 9.2, and a number of the utils were installed but not the default (e.g. automake). Create a directory to receive the source (I use /data/tuxbox-cvs for the source and /data/dream for the output as there isn't enough space in my /home mount) Then cd to your source directory and fetch the source: cvs -email@example.com:/cvs/tuxbox -z3 co -r rel_1_0_0 . don't miss that final '.' char at the end. Once the source has downloaded (only takes a few mins) you cd into the cdk directory. DO NOT ATTEMPT TO BUILD AS ROOT. Run the following (substitute directory names as required): ./autogen.sh ./configure --prefix=/data/dream --with-cvsdir=/data/tuxbox-cvs --with-targetruleset=flash --with-cpu=405 --disable-libcrypto --disable-flashmodutils --enable-maintainer-mode