You can get a free download of the game from various websites but I gather you are looking for the full version which you don't want to pay for. There may be ways to find this file on torrent sites but these can be illegal. If you really like the game then you should pay for it since the people developing it aren't just doing it for fun.
Virtual Villagers is a life simulation game, similar to The Sims developed and published by Last Day of Work first in 2006 but with numerous new releases since. The most recent of these is New Believers but others The Tree of Life, Secret City, The Lost Children and A New Home were also popular.
The games are all set on the island of Isola and through different starting points, see a group of settling villagers build towards a point of civilisation. This is achieved through a series of puzzles and keeping your villagers from starvation by leading them to sources of food.
In Virtual Villagers 3: Secret City, you embark on a mission to the northern shore of Isola and discover an abandoned city which you attempt to restore to its former glory and discover its secrets in a kind of Macchu Picchu meets Sim City.
The newest instalment, New Believers, released on 30th December 2010 differs slightly because there is a new religion element and it is closer to a 'God” game because the player is experiencing yourself as the creator with more influence than the tribe themselves.
The first edition of the game has won several awards and I suggest that if you want the developers to keep working on and improving the game with new releases then you will manage to put some money their way.