"Is this a pumpkin plant?"

Probably. Although there is no way to tell if it was cross pollinated or if the pumpkin it came from was a hybrid. So you might get something that looks completely different than the original. It will still be interesting though.

"Will it die in this 8-10 inch wide pot? Can it be transplanted?"

Squash grow and become rootbound quick. So yes, you need a bigger pot. I'd suggest something of at least 5 gallon size (which would be like the absolute bare minimum). And you'll need to transplant it as soon as possible to avoid disturbing it's roots. Cucurbits don't do well with transplanting but it will need to be done if you are going to have a chance at getting fruit.

"Will eastern light even sustain a pumpkin (full sun until 1pm)?"

It would do better with more light but you have to work with what you've got.

From what I can tell from the photo, the potting mix looks a little dry (maybe it's moist underneath the topmost layer; no way for me to know) and the leaves are pale. When you transplant it give it some fertilizer.

Rodney

A few years back I left a large uncarved Halloween pumpkin outside where it fell on the ground near our front porch. In the spring long before the last frost, I saw that dozens of seeds had sprouted. Many survived the freezes and even snow, so when the weather warmed up, I culled all but the two largest seedlings and mulched them with several inches of compost. It was in dappled shade with only a few hours of morning sun. I tried to train it to climb up a tomato cage, but after climbing to the top and back down again it began wandering into the lawn, chasing the sun. The vine grew another 15 feet and it began blooming profusely. The flowers were the size of dinner plates and quite beautiful. Toward the end of summer, it produced a couple pumpkins. They were the size of basketballs and still green when we had our first hard freeze. It was a great conversation piece. Since then I've tried purposefully growing pumpkins in whiskey barrels with good sun and fertilization, but never was able to produce another fruit.

Thanks for the responses. I had to pull it out as it was going to kill the nasturtium underneath.