mp_order post type. Is the author ID the Id of the person who purchased the item

Hi there

I am just working on a feedback plugin for marketpress. I am just working on a function making sure the purchasers bought items and the shops sold items match so that the purchaser is allowed to write feedback.

Ive found the mp_order post type and it includes a field for author ID.
Is the author ID the ID of the purchaser? I thought it might be as it isnt the ID of the blog user.

If someone purchases the product but isnt logged in, what is put in the author ID field?

I am tracing the data around in circles in phpadmin but thought it would be quicker to ask the question here...

ps the blog owners ID is "19" in the screenshot. The blue rectangle indicates the orders. The red circle is the author ID for one of the orders