I got the WooCommerce integration working for my registered product.
I was hoping to use it for my trial version as well, but I noticed that when the trial expires, instead of giving a link to purchase a new key, the Activate button is there. If you put in the original activation token that was emailed to the user for the trial, it activates it again for another free trial period. I presume that this could be done indefinitely.
This seems like a flaw in the integration to me. Is it supposed to work this way? The Key Generator does the same thing.