I can't imagine Game's Workshop having any problem with it as they have been extremely liberal with the use of their IP lately. Their new CEO is also pretty progressive, but I think the issue is whether or not if your message will fall into the bin of a thousand others.
Even if you did continue the mod without contacting Game's Workshop you are extremely low on their radar. They'd much rather target ****** spin-off games on the app store that are actually making money from their property. I'd also recommend trying to contact the creator of Galaxy At War & Winter Contingency to ask how they are getting around the copyright infringement. (But I understand your concerns.)
D∃ltɑ
joined
I do programming, and also play bass.