B - stands for BUILDS. This is the process of packaging up the source code in such a way that it can be easily deployed by the customer.
For the frontend (eg Angular) this involves running some kind of
For the backend (SAS) this would involve loading the source code into services (Stored Processes in SAS 9), creating the configuration process (eg to deploy the data model, perhaps with a html wizard), and compiling into an SPK (again, SAS 9 approach).
Combine that with some testing and documentation, and your app is ready to go!
There aren't many platforms that let you deploy web apps as easily as SAS. For an example, check out the video below.