I think I can now say that Jack is crawling. It's more like an army crawl right now, and he doesn't get very far very fast, but he does get to where he wants to go now! He's not aware that he can army crawl yet. When he sees something he wants, he bounces and leans forward, but doesn't want to fall to his belly yet. He hasn't caught on that if he falls to his belly, he will then be able to crawl to the desired toy. I'm sure it's just a matter of time.
The onset of my son crawling means I'm going to start crawling too - to baby proof the house. Although I could do it the lazy-mom's way. When he gets into something he's not supposed to get into, I'll know I have to move it up. Until then, everything stays as-is. I'm currently trying to do SOME baby proofing. We'll see how well I can look at my home with fresh, baby eyes.