I reckon that for your RAM starved system the dependency on 'Xorg' is the least of your worries: I did a quick test in a VM (QEMU with 128 MB RAM and a 300 MB virtual disk), downloaded 'K3B' to the disk (with tce-load -w k3b) and attempted to install it (with tce-load -i k3b).
I ran into all sorts of No space left on device issues, and that even after creation and use of a 96 MB swap file. As there were still a few MB left in the rootfs it dawned on me: this rootfs had run out of inodes, which where needed in '/tmp/tcloop' to install all those many files for all those many dependencies (BTW, this can be checked via /bin/df -i /).
Just to have a laugh I undertook another test, this time with a larger (virtual) disk (i.e. 800 MB): I booted with boot codes 'tce=hda1 local=hda1' (which is know as "hybrid mode" and means that all of '/usr/local' is on the disk). I then went on to download the 'k3b.tcz' extension (as above) and install it with copy to the file system (i.e. via tce-load -ic k3b). The outcome (after ca. 12 min it took to eventually get that far) was that it appeared that I was able to run 'k3b' whilst the 'Xvesa' server was still running.
So 'Xorg' might not really be required as such. But in my view this finding is neither here nor there as the next time one would boot the 'Xorg' X server would be used by default. OK, I'm aware of a way to "fudge" around this hard-coded rule in 'usr/bin/xsetup.sh' (e.g. via sudo mv /mnt/hda1/tclocal/bin/Xorg /mnt/hda1/tclocal/bin/Xorg-), but that is not really the point.
The point is that it is rather hard to come up with a setup which would maybe allow 'k3b' to be run on a RAM-starved system. Mind you the "hybrid mode" is not really been much of the focus recently, and I personally would not use it anyway. As it turns out there are several extensions (i.e. 'Xorg-7.5-lib.tcz', 'glibc_gconv.tcz', 'gudev-lib.tcz', and 'udev-lib.tcz') that contain shared libraries in '/usr/lib' and are therefor non-PPI compliant. Furthermore there are 10 extensions that have startup scripts, which IIRC are not run when installed in "hybrid mode" (and at least the one for 'dbus' really needs to be run). All this only makes it rather difficult, even for a knowledgeable user.
What are the alternatives? I'm not sure which GUI application to suggest as I use none of them. But searching with the help of 'appbrowser' I found (in alphabetical order and including there total size): bashburn.tcz 5.90 MB
brasero.tcz 24.16 MB
xcdroast-gtk1.tcz 2.71 MB
xcdroast-gtk2.tcz 9.73 MB
xfburn.tcz 19.90 MB
All but the last seem to be front-ends to 'cdrtools.tcz' (1.28 MB), which is incidentally the only extension I use to burn any CD-ROM images from TC. Sure it requires that one reads up about it's use (at least once), but I only ever need a few different options (e.g. '-verbose', '-scanbus', '-minfo', 'dev=...', 'speed=...' and 'blank=...') to manage my needs, so that in the end did not take much to effort to figure out.