"Mono is an open source implementation of the .Net development
framework as developed by Microsoft and submitted to the ECMA
standards authority. The project, which released version 1.0 last
month, is significant in several ways: it offers the potential to
unite the open source communities for Windows, Linux, and other
platforms; it fulfills the niche for a powerful migration tool; it
builds upon existing open source technologies such as Mozilla and
Apache; and--most importantly--it illustrates the resolve of the
open source community to rise to Microsoft's challenge.
"Mono provides a unique and significant opportunity to unite the
open source development communities for Windows, Linux, and other
platforms. Through its use of the C# language, Mono can develop
true cross-platform applications with ease..."