"Kevin" is correct from his perspective. Vegetable Sphaghetti is open pollinated, thus not a hybrid. It has been in continuous commercial production, so does not fit many peoples definition of "heirloom".

All Heirlooms are OP, but not all OP are Heirlooms.

To qualify as an Heirloom, the variety must have been around for at least 50 years. Some people only classify Heirlooms as over 100 years, others if the variety has some degree of history. And even that doesn't suffice. There are about as many "definitions" of what an Heirloom is as there are stars. (Alright, not quite that many...)

But, what everyone can agree upon is that all Heirlooms have to be OP. And, Spaghetti Squash, albeit having been around for a long, long time, there are different cultivars of it. And not all the OP cultivars are really that old. Some, however, I'd be willing to bet are over 100 years old...

A recent intro to the North America> Burpee 1936. They got it from Sakata.
"Vegetable spaghetti, as it is sometimes called, originated in China. It was introduced to Japan in 1921 by a Chinese agricultural research facility, according to the Kanda Seed Company. It was first sold commercially by the Sakata Seed Company of Japan; the Burpee Seed Company brought it to the United States in 1936, where it gained limited popularity. It was widely grown in Victory Gardens during World War II, but only became an American favorite during the late 20th century."

So Heirloom is like saying Organic.
Many different definitions, tar & coal are organic, but should not be put in the compost pile.
Great thread, informative feed back.
By the way I planted Spaghetti squash, one hill, one year & got 3 to 4 fruit on each vine.

Thanks much for all the help! I learned a lot. Ya'll are the Best!