PortMedia offers free, cross-platform, open-source I/O libraries for digital media including MIDI, video, and audio (see www.portaudio.com). Most work is in C to facilitate interoperabilty with many languages and systems.
Open source project that offer summary and download services on this page is a project that carry out their development work on other open source development sites. Their work is linked to this page via a feature called OFI, and their work is not carried out here on OSDN site.