FreePrince is a free (GPL2+) implementation of the DOS version of Prince of Persia 1.
Its official website can be found here.
There have been no official releases of FreePrince; it still needs a lot of work.
More complete reimplementations are SDLPoP and MININIM.
Download for Windows: FP_2006-11-11_Windows.zip (741KB)
Download source code: FP_2011-12-04_source.tar.gz (271KB)
Git repository: git://sdfg.com.ar/fp-git.git (web)
The main author of FreePrince is Enrique Calot.
Other authors are Rodrigo Campos Catelin, Diego Essaya and Ricardo Markiewicz.
Some development screenshots are available.