Thank you Jimmy. I will contact them. But just for reference, they do have a friendly looking Developers section at pdk/ . I'm totally new to this part so it's still kind of foreign to me.
Here's a quote from their first page on the subject..
SOAP-based Web Services platform allows you to deliver shipping labels to virtually any technology environment necessary. Ideal for web-based ecommerce integration or any web-hosted application.
so it looks promising.
The USPS Web Tools looks confusing to me already. I can't figure out if my client has to have a regular account with them AND a Web Tools account. Or if they are one in the same because it also mentions that a developer for someone else' site should register but then change it over later. I am assuming that is similar to PayPal's use of the Sandbox but it isn't clear.
I'll post back.