The D3sdk Support Site (temporary URL until the DNS on the actual site resolves) has the SDK (Software Development Kit) for Descent 3 available for download. The SDK contains files and information required to make alterations to the game and its Descent 3 Fusion Engine, and word on the page is "Hopefully we can help you unlock and create the most mind blowing mods to ever hit the multiplayer scene. The Sky is the Limit and we're here to help you get there." Thanks fathom from Descent.Org.