My understanding of dreadlocks are matted/locked hair.
That means regardless of whether the hair is your own hair, regardless of chemicals, regardless of age of style. Once they are matted or locked then they are dreadlocks.
I use this definition because you can not tell from looking the method of locking. And honestly, there are enough negative feelings about locks without there being division between people who have different types.
There are no "real" dreadlocks.
There are baby locks (start - 1 year), middle stage (2 - 3 years) locks, adult locks (4 years and up). But those stages are simply because the look of the hair is different. Baby dreads are less uniformed, temporary and can be combed out usually. Middle stage locks have begun locking, often bumpy because of the process and adult locks look like solid ropes of hair.
If I have chemical dreads or yarn dreads when they reach the adult stage you should not even be able to tell the difference. So why does it matter? This community is usually fairly open about people and their styles but occassionally people have derogatory comments about what makes someone's dreads unreal.
Dreads, in all their forms, are beautiful and we of all people should realize that.