how to download k3b???? well it depends on your distro doesn't it?
in slackware you got to www.linuxpackages.net
get k3b (there is a search tool top left) and dvd+rw-tools.
then upgradepkg --install-new *.tgz (while being root)
FC probably ships, but googling the two packages +"distro name" should also get you the proper downloads. Keep in mind a couple of things though:
if you are working of a boot disk, you may not be able to install software, or burn (especially if you only have one drive). In that case you might be better of to get a network connection (locally) and ftp into the linux box as a user that exists and then ftp the files you want.
Also, a USB stick might be reasonably painless.