In order to dual boot DSS V6 and another linux distro using Grub boot loader, you will need to create a menu.1st file for Grub, and specify the DSS V6 partition. This allows Grub to display DSS V6 as a boot choice, and allows DSS V6 to boot using its on boot loader from the install partition.

Add the following to /boot/grub/menu.1st
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Open-E DSS V6
root (hd0,1)
chainloader +1
boot
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The root partition line is the important part. Hard disks start at 0 = /dev/sda, 1 = /dev/sdb, etc. Partitions start at 0 also, so (0,0) = /dev/sda1, (0,1) = /dev/sda2, (1,3) = /dev/sdb4, etc.
This line needs to reflect where you have installed DSS V6.