Comment 6 for bug 324452

I see that Pendrivelinux.com has a couple of related webpages on this potential ability to install more than one distribution using Linux.

1st: MultiSystem – Create a MultiBoot USB from Linux
This requires an Ubuntu CD or USB and the downloadable and uncompressed install-depot-multiboot.sh shell script.

2nd: Boot Multiple ISO from USB via Grub2 using Linux
The Pendrivelinux.com author of the steps described in this webpage uses a running Ubuntu LiveCD to carry out very technical and manual procedures.
The author has apparently done the USB MULTIBOOT work for Ubuntu 10.10 IS0, Linux Mint 10 Gnome IS0, DBAN IS0, and TinyCore IS0.

Still, I also SECOND it for UNetbootin devs to make available a good and simpler way of enabling multiboot installation onto USB- drives/sticks from Linux.