The Golden Years (1990-2000)
The 1990's were the years when License Management really became accepted in the ISV community. From a start of fewer than 50 ISVs using commercial license management systems, by the end of the decade there were over 2000 ISVs shipping products with embedded commercial license managers. The adoption of license management, however, was primarily among vertical-market applications, as opposed to the more general desktop productivity applications.
In 1990, TCP/IP was primarily used on Unix systems, with Netware dominating on DOS systems, and a viable Windows OS still a few years off. Most commercial license managers were based on the TCP/IP stack. To the best of my knowledge, FLEXlm was the only license manager that used TCP, others used UDP or some kind of RPCs.
The early 1990's were a time of many system vendors building workstations and servers running one variant of Unix or another. I recall in the early 1990's supporting FLEXlm on over 40 Unix platforms. (The good news is that the Unix/Linux market has consolidated, and the vast majority of these systems are gone today.)
As the decade wore on, the users of license-managed software began to realize that there was value to them in having a license manager embedded in applications which they purchased. With an embedded license manager, end-users no longer needed to worry about keeping track of their license agreements to ensure that unlicensed users were not using the software - this was now built into the software they purchased. In addition, end-users were able to get usage data on purchased software, which enabled them to predict future software purchases and in some cases bill software usage to various departments within an organization.
As the decade wore on, license management capabilities for end-users became more and more sophisticated, allowing them finer control over how and where licenses were used.
Once end-users saw the advantages of a license manager, it moved from being a burden an ISV imposed on their customers to a more normal course of business. This, in turn, accelerated the adoption of License Management among ISVs.