AOL's participation would mark a change in the progress of the case. To date, amicus, or friend of the court, briefs, have been filed at various stages in the case by trade associations such as ProComp, the Software & Information Industry Association (SIIA), and the Computer & Communications Industry Association (CCIA).
Although Microsoft competitors are members of these organizations and partly fund them, rivals have avoided direct participation in the process. Currently, the Federal Trade Commission is examining AOL's proposed merger with Time Warner.
Both AOL and Microsoft declined to comment on the matter.
Amicus briefs are not mandatory. Instead, they exist to provide the court with advice or additional viewpoints. Microsoft's appeal is under the jurisdiction of the U.S. Court of Appeals for the District of Columbia Circuit.
The deadline for motions seeking to file amicus briefs supporting the government is Wednesday. In addition to AOL, the three trade associations--ProComp, SIIA and the CCIA--are expected to file motions.
Although four requests may be made, it is uncertain whether the court will allow four amicus briefs to be filed in the case. The court has strongly recommended that only one amicus brief for each side be filed.
The Department of Justice and 19 states are pressing the case against Microsoft, contending that the software giant violated antitrust law. The DOJ won the case at the trial level, which prompted Microsoft to file the appeal.