So I do not understand the original poster, or your response.
The purchase and and where to dowload is in the window when you buy it.
Also he is not an osTicket dev. He is an independent developer that sells a product that works with osTicket.
That being said when you make your purchase of the product (its done via paypal) and you click the button after finishing the purchase it takes you back to software-mods website and provides instructions on how to download.
Just to make sure I was right I've just bought the plugin from him again.
click Pay now.
Then click Return to Merchant.
You are presented with this page.
You can download the version of the plugin that you need for multiple versions of osTicket, and it provides instructions, and version release notes.