Social game company Zynga on Thursday filed a lawsuit against fellow game company Vostu for blatant copyright infringement, suggesting that Vostu exists only to create and release copies of popular Zynga titles.

Vostu is based in New York and has offices in São Paulo and Buenos Aires. It is currently fighting with rival company Mentez to become the Zynga of social games in Brazil. It most recently raised $30 million in funding from Accel Partners and Tiger Global Management.

Reggie Davis, General Counsel for Zynga, told TechCrunch:

“It is one thing to be inspired by Zynga games, but it is entirely different to copy all of our key product features, product strategy, branding, mission statement and employee benefits lock, stock and barrel. We welcome Vostu into the arena of social games, but blatant infringement of our creative works is not an acceptable business strategy—it is a violation of the law.”

The evidence against Vostu is significant. All of the games share a similar look, the same mechanics, and the same items. The screen cap below shows the similarities between Zynga’s Cafe World and Vostu’s Cafe Mania:

Not only has Vostu released copycat versions of FarmVille, Zynga Poker, PetVille, Cafe World, and CityVille, but Vostu even copied some mistakes in those games.

The lawsuit describes the error copying as such:

“Vostu’s copying includes “mistakes” in Zynga’s games. For example, in CityVille, the Zynga developers forgot to add the requirement that Community Buildings be connected to a road in order to function within the game – a requirement for all other buildings in the game. The game was released without that requirement, and the bug was never fixed in Zynga’s game. Vostu’s MegaCity replicated this “mistake.”

One funny thing to consider here is that Zynga has a history itself of copying games and getting away with it. Back when the incredibly popular FarmVille debuted in June 2009, another Facebook game called Farm Town was popular. Farm Town had trouble keeping up with its user demand, so FarmVille came in with an extremely similar title and took nearly all of Farm Town’s fans. FarmVille now has 42.5 million active users while Farm Town has just 1.7 million.

In a statement to VentureBeat, Vostu spokesperson Davidson Goldin called Zynga’s lawsuit frivolous:

“Zynga has been accused of copying so many games that they’ve sadly lost the ability to recognize games like ours that are chock full of original content and have been independently created. Vostu has 500 brilliant employees working night and day making hand drawings and writing proprietary code for online games that our 35 million users worldwide enjoy. Zynga’s anti-competitive effort to bully us with a frivolous lawsuit — especially when we have some of the same key investors — is pathetic. While Zynga plays games with the legal process we will continue focusing on using our substantial resources to create games that entertain our customers.”

If you really want to think about game copying in full context, consider that many of the titles being brought up are essentially copies of old game franchises with a social twist. FarmVille and Farm Town resemble Chinese farm games, which themselves may be clones of the Harvest Moon series, and games like Zynga’s CityVille and Vostu’s MegaCity are clones of the SimCity series.

What do you think about game copying? Do you think Vostu deserves to be sued?