Virginia-based Rosetta Stone Inc., maker of the language-learning software firm has filed a lawsuit against Google Inc., alleging that a change in Google's policy assists the unauthorized use of its brand by competitors and software pirates.

According to Rosetta Stone Google's changed AdWords advertising policy permit advertisers use its trademark or similar terms in the ad text even if they don't possess the trademark or approval for the same.

Rosetta Stone argues that rivals and other companies can use its brand name as key words and include them in the ad's text divert people to their Web sites, making Google coin money from the transactions.

On the other hand, Andrew Pederson, Google spokesman they let trademarks to be used as keyword triggers in AdWords because this enables a user to choose from a lot of competing advertisers. It's as normal as a magazine to publish Ford ads opposite to an article about Toyota. He further added that to limit competition online by restricting the number of choices available to users would not make sense.

In the recent trading, Rosetta Stone soared to $26.23, up 13 cents, while Google closed at $414.40, up $4.01.