The latest prerelease is available at
http://www.arcengames.com/share/AIWar1999S.zipThat version is an upgrade from version 1.301, so you have to already have 1.301 (or greater) installed. Just unzip it into your game folder (usually C:\Program Files\Arcen Games\AI War\ unless you specified something else). Please make sure that your unzip process keeps the folder structure from the zip file, rather than just unpacking all of the files into the base target directory.
What's new since 1999R:
(Cumulative release notes since 1.301 are attached at the bottom)
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-Starship Constructors now use the same icon as space docks in far zoom, rather than the icon used by mobile builders. Starship Constructors have a "Star" label under themselves, and now show up separately on the planetary summary sidebar, which makes selecting groups of mobile builders or starship construcotrs much simpler.
-There was previously a bug when tugs had tractored a ship that escaped to a new planet just as the other ship was being tractored. Fixed.
-A new keyboard shortcut has been added: Shift+F3 now shows network debug info, including dropped/resent packets, etc. This is crucial for debugging poor network performance.
-Previously, on some connections the performance when loading a savegame across the network was really poor (and in a few edge cases, ridiculously extremely poor). This was due to packet loss rates, and partly due to the network adapter incorrectly being flooded by the network library we use. Fixed.