The Mono Project

Background.
The GNOME project goal was to bring missing technologies to Unix and make it competitive in the current market place for desktop applications. We also realized early on that language independence was important, and that is why GNOME APIs were coded using a standard that allowed the APIs to be easily wrapped for other languages. Our APIs are available to most programming languages on Unix (Perl, Python, Scheme, C++, Objective-C, Ada).
Later on we decided to use better methods for encapsulating our APIs, and we started to use CORBA to define interfaces to components. We complemented it with policy and a set of standard GNOME interfaces for easily creating reusable, language independent components, controls and compound documents. This technology is known as Bonobo. Interfaces to Bonobo exist for C, Perl, Python, and Java.
CORBA is good when you define coarse interfaces, and most Bonobo interfaces are coarse. The only problem is that Bonobo/CORBA interfaces are not good for small interfaces. For example, an XML parsing Bonobo/CORBA component would be inefficient compared to a C API.