QuickBBS
A late-1980s DOS bulletin board that was fast and easy to set up, and spawned so many clones that its file formats outlived the program.
Adam Hudson wrote it in Pascal and gave it a message base in which every conference shared one set of files — the format that later took his name. For a FidoNet sysop running a single 286, that was the right trade-off: few files to open, short seek times, and a tosser that could write straight into the base.
Its success turned the formats into a de facto standard. RemoteAccess began in 1989 as a QuickBBS-compatible alternative, and SuperBBS and others read the same files. Sysops could switch software without users noticing — an early form of vendor independence that existed mainly because nobody wanted to spend a Saturday night converting databases.