I looked up vegetable leather and from what I am reading it appears that it means the leather is vegetable-tanned. I would love it if it meant vegan-friendly, though. Kristine, I couldn't find the site you mentioned.
I notice that in addition to discussing the vegetable leather in the beginning, the description also mentions a "breathable leather and fabric sock lining." So even if the shaft isn't real leather, it sounds like there might be some leather component.
I would be interested to hear what Zappos says or if you buy the boots, what the label says. Like Frances, sometimes I find the materials used to make shoes are not properly listed on websites. One time I actually called Steve Madden to ask them about the components of a specific shoe and they said it was all man-made, but when it arrived, it had a leather sole and leather lining, and was labeled as such on the shoe. It was really disappointing. I really like the boots, and since I don't purchase leather at all, it would be great if they are vegan!