Blend2D is not a single monolithic library. It's a project that splits itself into smaller libraries that are all used by the main product called b2d. The blend2d organization on github covers b2d and all other libraries that are part of the whole Blend2D project.
B2d is the main product of Blend2D project. It provides a high-level API that targets 2D vector drawing. The b2d library uses all other low-level libraries internally and doesn't expose them to its users.
(b2d library will be open-sourced soon)
B2dPipe is a 2D pipeline compiler developed as a part of Blend2D project. This is a very low-level library that can be easily used by other 2D engines to create the same pipelines as used by Blend2D. B2dPipe is not a rendering engine and it doesn't provide any kind of rendering context, it just constructs pipelines and defines structures that are used by them.
AsmJit is a complete JIT and remote assembler written in C++. It's a backend that B2dPipe uses to emit machine-code. AsmJit is very close to Blend2D project, but it's not an official part of it.
(will be updated after b2d is released, b2dpipe contains build instructions on github page.