The Pakfire builder is designed to be a modular system and not to rebuild the whole distribution over and over again. Overall build time of the IPFire-2.x distribution takes several hours and is not very easy to maintain.
The builder downloads dependencies and essential tools for the build process automatically, extracts them to a temporary environment and build the package(s) within this environment. Every environment is completely distinct from an other and not related to the host system at any point. Thus, the host system is not harmed in any case.
Pakfire is able to handle multiple repositories. So it will be possible to add development repositories or any other third party repository, if one will be available in the future.
For every build action, a clean build environment is created. For that, all the essential packages to run a build system are extracted into a directory. Then, the build process chroots into that directory and either the build process or a shell is started - as if it was running on a freshly installed IPFire system.