Google is paying $106.5m (£64m) for , which makes video compression software. However On2 has revealed that it has been served with two class action complaints.
Both suits aim to block the deal and allege that On2's board has "breached their fiduciary duties to the stockholders of the company in connection with negotiating and entering into the previously disclosed merger agreement with Google".
The dispute centres on the fact that although Google's offer of 60 cents (36.3p) per share represents a premium of 57% on the On2 share price the day before the deal was announced, it does not reflect the price that shares in the company were trading at in the months before the deal.
On2 says that it intends to "vigorously contest such allegations". If the deal goes ahead, it will be the first time that Google has bought another publicly listed company.