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The owner, originally, is the person who purchases the licence in the shop.
The owner can:
Use the licence on their own.
When you buy a licence your email also appears in the "Assigned to" field. So the licence is assigned to the owner by default.
Example: Rinoa bought the GiD 16 licence from the shop. She is the owner of the licence and it's also assigned to her.
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Change the licence assignation.
The owner still has control of the licence but can assign it to another person.
Please note that you can change the assignation at any moment, also in the middle of the active period, this will not be affected by the change.
Example: Rinoa is the owner of the licence but has assigned it to Squall. Now Squall is the one who can use the licence.
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Change the licence owner.
The owner can also change the ownership in favour of another person, but this change will trigger that the licence will disappear from their Licence Manager and he/she will lose control of the licence.
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The assigned is the person who has permission to use a licence.
The assigned can:
Use the licence, he.
He/she can not reassign the licence to another person.
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