All games are going to have overlapping concepts/systems, it's just the limitation of the system and the genres. There's varying levels of similarities between games, and while no one will cry foul over two games both having a system where you battle monsters and gain exp, who's to say at what level of similarity someone will become suspicious at?
I think because of that, even though I trust everyone involved completely, in order to remove any suspicion we should keep playable builds private until the final release. That way there's no way there can be any form of theft, and any similarities will be coincidence or just due to similarity of the programming and genres.
For gameplay updates, or if you just have to show off a system/scene for publicity, I think we should limit it to screenshots and videos.
There is absolutely no way we can prevent each other's games from impacting one another on some level, but you have it from me that, in the interest of the community having a varied experience between the two games, if I make any changes in response to your guild's work, it'll be to diversify our project from it.
There...I was long-winded.