The build versus buy licensing dilemma is the oldest debate in the industry. After all, managing the licensing of your software is an important aspect of any commercial application, but it is not the core product you are selling.
The build vs. buy debate centers around the balance between providing the features and functionality your customers want in your software, with your need to protect access to your software through licensing systems. Developers approach this strategically and smartly, and prefer to not reinvent the wheel, utilizing libraries, previously written code, and third party services to provide the license scaffolding around the software solution.