Fubsy is a tool for efficiently building software. In concrete terms, it lets you conditionally (re)build targets from sources based on which sources have changed since the last build. Typically, targets and sources are all files in a directory tree. In theory, they can be any resource on a computer. More abstractly, Fubsy is an engine for conditional execution of actions based on the dependencies between related resources.
Upmf is a source-based package manager written almost completely in Scheme. The user is able to search, build, and remove packages. Since Scheme through GUILE is very extensible, the user can customize the procedures, or even exchange them with his own, if wanted. Packages are stored in their own self-contained directories and are incorporated into the filesystem with help of GNU Stow.