You'll need to buy the game in order to join Offical servers! This is alpha v0.07, version is OUTDATED, get 0.90 instead, it is full version of 0.09 that means you don't need patches or anything, just download it, extract it using program like winrar and you are ready to go
Fixing style that this version is old & outdated. Do not download this early version, as you will find no servers for it. Current version is Full Invasion 2 v0121 released December 25th, 2014. This is a multiplayer only modification.