The 0MQ lightweight messaging kernel is a library which extends the standard socket interfaces with features traditionally provided by specialized messaging middleware products. 0MQ sockets provide an abstraction of asynchronous message queues, multiple messaging patterns, message filtering (subscriptions), seamless access to multiple transport protocols, and more.
4DIAC is a framework for distributed industrial automation and control. It aims to provide an open, IEC-61499-compliant basis that lets the user establish a distributed industrial automation and control environment based on the targets' portability, configurability, and interoperability.
4Pane is a four pane detailed-list file manager for Linux. It is designed to be fully-featured without bloat, and aims for speed rather than visual effects. In addition to standard file manager things, it offers multiple undo and redo of most operations (including deletions), archive management including 'virtual browsing' inside archives, multiple renaming/duplication of files, a terminal emulator, and user-defined tools.