| Online Travel Agency System Project | 1 | 9 |
| Online Tutor Portal Site Project | 1 | 2 |
| Online Tv Database Project | 1 | 1 |
| Online Web Building | 1 | 1 |
| Onlinegrades | 1 | 5 |
| Onlineonly | 1 | 1 |
| Onlinetechtools.com | 4 | 5 |
| Onlinetools | 1 | 1 |
| Onlinetools.org | 1 | 2 |
| Onlyoffice | 5 | 163 |
| Onlyscript.info | 1 | 2 |
| Onnogroen | 1 | 2 |
| Onnuri Infotek | 1 | 4 |
| Ono Oogami | 1 | 1 |
| Onosproject | 1 | 27 |
| Onpremise SureMDM Solution | 1 | 1 |
| Ontarioabandonedplaces | 1 | 1 |
| Ontariosystems | 4 | 4 |
| Onthegosystems | 1 | 2 |
| Ontrack Project | 1 | 1 |
| Ontraport | 1 | 1 |
| Onworks | 1 | 1 |
| Onyaktech Comments Pro Project | 1 | 2 |
| Onyxforum Project | 1 | 1 |
| Ooapp | 1 | 1 |
| Oocomments | 1 | 1 |
| Oodie | 1 | 1 |
| Oomphinc | 1 | 1 |
| Ooorl Project | 1 | 1 |
| Ooso | 1 | 1 |
| Oovoo | 1 | 1 |
| Op-browser Project | 1 | 1 |
| Op-tee | 1 | 1 |
| Op5 | 3 | 11 |
| Op\'art Save Cart Project | 1 | 1 |
| Opac Project | 1 | 1 |
| Opalvoip | 1 | 1 |
| Opart | 1 | 1 |
| Opartfaq Project | 1 | 1 |
| Opayweb | 1 | 1 |
| Opc Ua Stack Project | 1 | 2 |
| Opcfoundation | 13 | 31 |
| Opcsystems | 2 | 3 |
| Opcua Project | 1 | 2 |
| Open Automation Software | 1 | 16 |
| Open Babel | 1 | 14 |
| Open Build Service | 1 | 14 |
| Open Dental | 1 | 3 |
| Open Design Alliance | 2 | 2 |
| Open Information Security Foundation | 1 | 33 |
| Open Mainframe Project | 1 | 2 |
| Open Robotics | 1 | 1 |
| Open Shortest Path First (OSPF) | 1 | 1 |
| Open Source Solution Technology Corporation | 1 | 3 |
| Open-Xchange | 2 | 16 |
| Open-audit | 1 | 22 |
| Open-blog | 1 | 1 |
| Open-classifieds | 1 | 1 |
| Open-emr | 1 | 97 |
| Open-falcon | 2 | 6 |
| Open-ftpd | 1 | 1 |
| Open-gorotto | 1 | 1 |
| Open-graph Project | 1 | 1 |
| Open-iscsi Project | 1 | 3 |
| Open-medium | 1 | 1 |
| Open-mpi | 1 | 1 |
| Open-realty | 1 | 5 |
| Open-school | 1 | 5 |
| Open-systems | 1 | 1 |
| Open-uri-cached Project | 1 | 1 |
| Open-xchange | 12 | 216 |
| Open-xchange Ox Guard | 1 | 1 |
| Open.edx | 1 | 1 |
| Open.gl Project | 1 | 1 |
| Open5GS | 1 | 8 |
| Open5gs | 1 | 11 |
| Open62541 | 1 | 2 |
| OpenACS | 1 | 1 |
| OpenAM Consortium | 2 | 4 |
| OpenAM Consortium | 2 | 2 |
| OpenAPITools | 1 | 3 |
| OpenBMC Project | 1 | 3 |
| OpenCV | 1 | 2 |
| OpenClinica | 1 | 2 |
| OpenCloudOS | 1 | 1 |
| OpenCycleCompass | 1 | 1 |
| OpenDDS | 1 | 5 |
| OpenDNS | 1 | 2 |
| OpenDayLight | 1 | 1 |
| OpenEMR | 1 | 1 |
| OpenEnergyMonitor Project | 1 | 4 |
| OpenHarmony | 1 | 38 |
| OpenIDC | 3 | 13 |
| OpenIdentityPlatform | 1 | 3 |
| OpenImageIO Project | 1 | 28 |
| OpenJDK, OracleJDK | 2 | 2 |
| OpenKM | 3 | 5 |
| OpenMRS | 4 | 8 |
| OpenMage | 1 | 19 |
| OpenModelica | 1 | 1 |
