Even though this post is old. It is the biggest sticky topic on the game out here. So i'll use this post too to make known that V1.5 has been fully released a while ago.
Since any patch above V1.4 is an unofficial fanpatch/community mod, both GoG and Steam do not sell the game updated beyond V1.4. We have contacted them a few times over the years and so far have not gotten anywhere yet.
Without our Discord community and our patches, the game couldn't even be sold as Multiplayer game anymore. So both stores are basically freeloading on our hard work.
Discord: Giants Discord Community
Steam Guide: V1.5 Techsupport and Multiplayer Guide