Insert witty/insightful opening sentence here.

Taking place 15 years after the GXP saga, Kenshi Masaki finds himself in Geminar, a world at war involving mechanoids. With his other world physiology being far superior to Geminars, he starts off on the wrong side but after he fails to assassinate Princess Lashara, he gets captured but instead of putting him to death, the crafty princess uses him as an attendant as she feels making him an ally would turn the tide of war in her favour especially when his nice guy persona coupled with his superior abilities makes him the perfect worker but this being a Tenchi Muyo anime, it's clear all the girls fall for him.
I'll just come out and say this, this isn't my Tenchi Muyo. In Tenchi Muyo the series' broken sci fi setting was saved by some really well designed characters, War on Geminar has really poor substitutes for those characters and it's lengthy run time per episode is packed full of filler that serves only to remind you of the franchise it's from. In the end you feel duped because you feel like you got something trying to copy Tenchi Muyo instead of it being a new season of Tenchi Muyo and it's not the first time this has happened.
All that aside can it stand up on it's own without the franchise tag? ummm kinda? It's hit or miss. Kenshi lacks a personality beyond being too nice while many of the girls can easily be pigeon holed into harem types, it's only real saving grace is the universe of Geminar beyond the huge spaceship is much more interesting but rarely gets explored.
A dub exists, I've not seen it but harem dubs rarely produce decent dubs anyway without hearing some very stock voices from the female cast.
Final Verdict: War on Geminar struggles with the Tenchi formula it inherited through being part of the same franchise. The characters are bland, the world outside the ship is way more interesting and the episodes are way too long to stay focussed on.