| Open Systems Technologies, Inc. | New York |
| Open Technology Development, LLC | Arizona |
| Open Technology Group, Inc. | Virginia |
| Open Technology Group, Inc. | North Carolina |
| Open Tier Systems | Pennsylvania |
| Open To Buy Wizard | Arizona |
| Open Universal Machine Intelligence | |
| Open Weaver | New York |
| Open Weaver, Inc. | New York |
| Open Web Application Security Project | Maryland |
| Open Window Software | Arizona |
| Open World Media | Indiana |
| Open-E, Inc. | Georgia |
| OpenAccess Network Services | Washington |
| OpenAI | California |
| OpenAPI Initiative | |
| OpenArc | Pennsylvania |
| Openbase | New Hampshire |
| OpenBCI | |
| OpenBench, Inc. | |
| OpenBrand | |
| OpenBucks | |
| Opencasa, Inc. | Florida |
| OpenCell Technologies | Missouri |
| OpenClass, LLC | |
| OpenClinica, LLC | |
| OpenClovis | California |
| OpenCom, Inc. | Iowa |
| OpenComps, LLC | |
| OpenCV | |
| OpenDaylight Project | |
| OpenDNS | California |
| Opendoor | Oregon |
| OpenDrive | California |
| OpenEdge | Utah |
| OpenEMR Foundation, Inc. | |
| OpenEnvoy | California |
| OpenEvidence | Florida |
| OpenExchange, Inc. | Massachusetts |
| Openeye Scientific Software, Inc. | New Mexico |
| Openforce | |
| OpenForge | |
| OpenGate Software, Inc. | Colorado |
| Opengear, Inc. | Utah |
| OpenGL | Oregon |
| OpenGov, Inc. | California |
| OpeningDesign | |
| OpenJaus, LLC | Florida |
| OpenJournalSystems.com | Arizona |
| OpenJS Foundation | California |