SO, I'm playing, and enjoying, though using dgvoodoo to get the game to fill screen seems to have had a knock-on effect where the z-buffer or sort ordering isn;'t right (I can see parts through ships).

My memory of I-War is that the software render was pretty nice anyway, so is it possible to get the deluxe version to run the software renderer?

You can try, but I'm not sure if it'll work. Just create a direct shortcut to IWar.exe without any command line parameters. You may find it doesn't work in full-screen, but it'll work in a window. To run in a window add -w to the target line in the shortcut.

There was a bug in the game where it could run much faster than 100fps in software mode on fast pcs, which broke the games timing system, causing collision issues, so you may encounter that in software mode. (When the game was developed 25fps was considered fast).