What happened to PayPal eCommerce Toolkit for Expression Web?
Lots of links around the web, all dead ends.
From PayPal Developer Central
For the time being, we are not offering the Expression Web line of products. The currant version of Expression Web does not include support for Add Ins. Microsoft is planning to release an update that will support add ins. once that update is released we will reevaluate the Expression Web line of products.