I bought this bonsai at Territory Days (Colorado festival) yesterday. I think the vendor said it was azalea or bougainvillea, but i don't remember which. Can someone identify it from this photo? Thanks.

It is not Azalea, so probably Bouganvillea but it won't be for long if you keep it inside. It will need protection in the winter from frost in a frost free greenhouse.

It doesn't have any thorns, though; I guess there are some varieties without thorns? I have it sitting now in an east-facing and open window, where it will get 4 or 5 hours of direct sun this time of year. Will that be enough? I could place it in a south window. Thanks for help.

Trees do best in an environment close to what they evolved in. A bougainvillea evolved with sun 10-14 hours a day, not blocked by glass. It evolved with temperature changes from day to night and with pretty high humidity, accompanied by lots of rainfall.

It won't get enough sunlight indoors to thrive. The humidity is probably not going to be high enough, and you probably won't water it like rainfall.

In other words, it won't do very well indoors all year.

I live in the Colorado mountains, so the outside humidity is not much higher than inside. I'll have to make do with a mister. On the other hand, we don't lack for sunshine! Thanks again.