It's now been patched for multiplayer (for those interested):
Rebellion's boss promised the Steam re-release of 1999's original Aliens vs. Predator would support multiplayer. They've delivered, patching in the support for that today.
Here's what it will and won't do:
• Integrated with Steam Overlay
• Uses Steam name
• Host/Join games via bare-bones in-game lobby browser
• Can invite and join friends and others via the Steam overlay
• Game attempts host migration
• Dedicated servers are not supported or planned
Multiplayer Patched Into Original Aliens vs. Predator Re-Release - aliens vs. predator - Kotaku