When did the internet become a commercial product?

The first private internet service providers (ISPs) began to emerge in the late 1980s and early 1990s. However, it was not until 1991 that a series of agreements made it possible for traffic from private ISPs to traverse the full breadth of the Internet "backbone," which was then maintained by the National Science Foundation (NSF), with government funds and therefore subject to a fairly rigorous acceptable use policy that generally forbade all but educational and research uses. E-commerce took hold in a limited way from 1991 onward but 1995 is when the Internet really took off as a fully private and commercial venture--this was the year that the NSF withdrew its support from the Internet backbone, turning it over to private control and therefore universally lifting anti-commercial acceptable use policies; that Internet registrar Network Solutions was allowed to charge for registering domain names; and that credit card encryption made large-scale e-commerce both practical and appealing to consumers. Add in the introduction of Netscape, which was, after Mosaic, the second widely available web browser with a graphical user interface (GUI) in 1994 (and a smash hit), and you had all the ingredients in place for the .com boom that occupied the rest of the 1990s. So the answer to your question is: it started in the late 1980s in a limited way, picked up steam in the early 1990s, and was fully realized in 1995--though saying that the Internet became "a commercial product" is not really an accurate way of putting it; the Internet does not properly refer to a product of any sort but rather the infrastructure and protocols (largely TCP/IP) that make seamless interconnection of multiple networks possible.