RULE (Run Up-to-Date Linux Everywhere) was a project that aimed to use up-to-date Linux software on old PCs (5 years or older) by recompiling and modifying some of the code in recent programs to make them use fewer resources, allowing them to run more smoothly and efficiently. 
Activity around the RULE project almost came to a complete halt in 2006, and in 2009, the project's head developer initiated an effort to clean up and freeze the project and its website. This was done to keep the completed project available in a tidy manner.
As of now (April 2023) the project is freezed with no activity surrounding the RULE project since October 2010.
Usecases.
The principal advantages of using old PCs with up to date software are: