| ID | Name | Type |
|---|---|---|
| #10583 | Onspec Software | Z |
| #10584 | OpalSoft | Z |
| #10585 | Open University | Z |
| #10586 | Opera Soft S.A. | Z |
| #21358 | Oporto BBS | P |
| #10587 | Optical Brothers | Z |
| #10588 | Optical Illusions | Z |
| #10589 | Optimal Group | Z |
| #10590 | Optimus Software | Z |
| #10591 | Options International | Z |
| #10592 | Opus Supplies Ltd | P |
| #10593 | Orange Enterprizes | Z |
| #10594 | Orange Software | Z |
| #10595 | Orb | ? |
| #10596 | Orbis Publishing Ltd | Z |
| #21563 | Orbit Data | Z |
| #18368 | Orbyte | P |
| #18306 | Orbyte Software | P |
| #10597 | Orc | ? |
| #10598 | Organism | ? |