1) Linux: August 25, 1991: There were thousands of open-source programs before Linus Torvalds wrote “I’m doing a (free) operating system (just a hobby, won’t be big and professional like gnu) for 386(486) AT clones.” to the Minix Usenet group and unknowingly started the operating system juggernaut that became Linux. That said, Linux has also become the most successful of open-source programs.
Linux has become the foundation for the Internet; the operating system for super-computers; and, thanks to Android, it’s becoming the most popular end-user operating system of all. There were indeed other free software programs being released in 1991 and earlier, but none would be more important.
2) Python: February 20, 1991: Guido van Rossum, Python’s creator, began work on this important language in December 1989. It wasn’t until February 1991, that it was released. Since then, according to Black Duck Software’s Ohloh programming statistics, “Python is the fastest growing language in the open source world as measured by number of contributors.”
It’s not just open-source developers that support Python. Even Microsoft provides a Python IDE (integrated development environment ) for Visual Studio.