Of course! All I ask is that if you post the drawing on dA, to add a link back to the stock picture if you've heavily referenced it (if you use it in combination with other references to create a different pose then you don't need to... )
Thank you! I would love to see the finished piece too!
And the non-commercial part is more in consideration for something like use by a business in promotional material or something... basically nothing that is going to make somebody a lot of money. I don't really mind my stock being used as references for commissioned drawings though.