Relics of Annorath.
The fantasy shindig is accepting alpha signups, but more interesting for the purposes of this news post is a selection of gameplay vids viewable via YouTube. Judging by said clips, seasonal changes and realistic weather are an integral part the game (also, rock slides). Relics of Annorath's website touts native Linux support and complex economic, guild, faction, and political systems. We've embedded a six-minute tech demo teaser after the break.
[Thanks to Paul for the tip!]