Companies

• Ongakukan
• Onion Games
• Onion Soup Interactive
• On-Line Entertainment Ltd.
• OnSkull Games
• On Target Simulations
• Oovee® Game Studios
• Opal Games
• Opaque Space
• Open Alpha
• open-source model
• OperaHouse
• Opera Soft
• Opera Software
• Operations Research Office
• OP Productions LLC
• Optik Software
• Optimum Resource
• Optobyte
• Orachi
• Orange Games
• OrangePixel
• Orbital Knight
• Orbital Media
• ORCA
• Orcsoft
• Orgesta
• Origame Digital
• Origamihero Games
• Origin Systems