WINE
Wine is an Open Source implementation of the Windows API on top of X and Unix. Think of Wine as a compatibility layer for running Windows programs. Wine does not require Microsoft Windows, as it is a completely free alternative implementation of the Windows API consisting of 100% non-Microsoft code, however Wine can optionally use native Windows DLLs if they are available. Wine provides both a development toolkit for porting Windows source code to Unix as well as a program loader, allowing many unmodified Windows programs to run on x86-based Unixes, including Linux, FreeBSD, and Solaris.
Relation to ReactOS
ReactOS has a relationship to the Wine Project.
From ReactOS's Main Page:
ReactOS has always planned to work with the WINE project to share as much programming effort as possible. This will mainly concern user mode DLLs and will happen once ReactOS's kernel mode areas are more complete, as those areas form the underlying infrastructure. Other areas of cooperation lie in applications and testing suites.
