I wouldn't put too much faith in that site. Although much of the information that was provided regarding California state law was accurate, it was very misleading regarding "dirks and daggers".
I offer the following only for the sake of clarification- That site gives the impression that anything that anyone might call a dirk or dagger is illegal, but the reality is that CA law specifically defines what it means by "dirks and daggers". Under CA law, a "dirk or dagger" is defined as "any item, with or without a hand guard, that is capable of ready use as a stabbing weapon", and only the concealed carry of such items is illegal. Any item, carried concealed, that can be "readily used as a stabbing weapon", not limited to but including- all fixed-blades, an icepick, a sharpened screwdriver, a folding knife with the blade opened and locked into position, etc, etc, are considered "dirks and daggers" under CA law.
Most people would define a "dirk or dagger" in the classical sense- as a knife with a double-edged blade, but that is not how CA law defines such items. In fact, there is no mention anywhere in CA law of double-edged blades. As a result, the open carry of a double-edged fixed-blade, and the concealed carry of a double-edged folder, are perfectly legal.
That site says that bowie knives are legal. And while it is true that it is legal to openly carry a bowie knife (I do it myself), if a bowie knife were carried in a concealed manner it would then be considered a "dirk or dagger" under the law, and would therefore be illegal.
I don't know who does the writing for that site, but I get all of my legal information regarding knives from a highly experienced criminal defense attorney here in California. I've had four such attorneys in my life here in CA, and they have all told me the same things regarding CA knife laws. As always, be wary of free legal advice found on the internet.
For specific information regarding "dirks and daggers" under California state law (as described in this post), people should read CA penal code sections 16470, 16590, and 21390.