Comment Open-AudIT (Score 3, Informative) 251
Open-AudIT is pretty good for cross platform but it doesn't cover all of your requirements. I'm yet to find anything that is an IP database plus complete system inventory.
Open-AudIT is very good at the inventory side. I run it in Windows since I was trying to replace TrackIT. There's a Linux agent and it'd be pretty easy to customize it for other OSes. It does licensing as well. Want to know how many computers have Office and what version? Who has outdated Antivirus? It even gives you license keys used. Getting it up and running with XAMPP for Windows is quick for testing. I haven't used it as much on the server side. We use IBM Director for that.