The difference is explained here: Yu-Gi-Oh! TCG Product Errors
Note that the above link is not an official source. Basically the difference is the “(if any)” which is not in the OCG text. These are due to clarifications that are added after translating from the official Japanese text. However, there is really no difference - you should be able to activate Seal of Orichalcos with or without controlling any Special Summoned monsters.