Which Product to Choose
BoxedApp SDK is a library for developers who want to emulate the file system and registry, run processes by loading them directly from the memory, use ActiveX without actually registering in the registry, and so on. Thus, BoxedApp SDK is a great choice for application developers (See also: Typical use scenarios for BoxedApp SDK).
BoxedApp Packer is an executable file packer solution. Use it the files to be packaged are known. You can use BoxedApp Packer for turning your or a third-party application into a portable application. BoxedApp Packer does not require the source code of the application; it deals with the binary executable files. The result of BoxedApp Packer's performance is an executable binary file that contains all the source files in the packed form. When started, the compressed files are extracted and placed in a virtual environment, so the application runs exactly as the original application would run if the files actually existed on the disk.
If your goal is to create a packer, use BoxedApp Packer API (BoxedApp Packer uses this API).
All the products in the BoxedApp line of products use the same technology, which supports virtual environment.