From what I've gathered from guild chat & on mumble, you are safe if you are below 45. As of a few days ago, there is not an upkeep on the guild war. We were at war with Spaghetti guild for several days. Also, the A-Hole guild on Edan "Gravity" is at war with about a dozen guilds.

Pre-launch, I read the same thing you did about there both being a war upkeep and all levels of guildies being fair game but I don't think that's the case right now. I'm not 100% but I'm pretty sure. I'll ask and see what the guild says.