I guess it depends on who you're talking to. In the minds of those same "traditional rabbis" any religion that isn't at least two thousand years old is a cult, and even that's being generous.
But, as with any body of knowledge, when something has been around long enough offshoots and adaptations will naturally form and you get many different traditions, each claiming to be "the one." Since we can't tell for certain what is the "true" Kabbalah, we can go to the history books and trace its lineage from there, although that in itself doesn't give much of an answer. Kabbalah probably began from
Merkabah mysticism which was (probably, maybe) the formal beginnings of proper Jewish mysticism, around 800 BC. Things get fuzzy after that, but we do know that the Zohar was published in the 13th century by Moses de Leon, and was "ascribed" to Rabbi Shimon bar Yochai who lived around the destruction of the Second Temple. It's probable he didn't actually write it, most occultists claim ancient lineages and authority.
In any case, what we know as "modern traditional Kabbalah" probably dates back to the 16th century with a new interpretation written by Rabbi Isaac Luria.
The history is muddled, of course, because different things were happening in different places of the world at once, and it was only later that different writings were codified into canon. It doesn't take Hermetic Qabalah into consideration, which began during the Renaissance as an offshoot of Christian Qabalah...
Anyway... since, as Aeon said, there's really no objective "original" version, anything is always a variation or adaptation. The Golden Dawn didn't take something original and then changed it, but rather adapted a version that was by then in vogue for several centuries.