Open Source is a global community of passionate and talented developers building best of breed applications often in response to inferior or restrictive proprietary alternatives, but mostly because of their passion for software and the individuals it attracts.
This creates a software ecosystem where only the strongest software survies and receive the most developer activeity, inferior software tends to become abandoned and obsolete.
The open source licenses are what allow this ecosystem to exist, it protectes the software and the authors of that software from others abusing their work. Their leagal implications ensure parties play fair.
The licenses There are orver 50 approved opensource licenses available. But the main ones you'll see are GPL, LGPL, Apache, BSD, and MIT, and the MPL. The most publiciced Licenese is the GPL. This says that code licensed under the GPL, or any code that uses or is drived from this code must reminan under the GPL license and if that work is distributed you must make available the modified source code. This is considered the foundation of most opensource projects including the Linux operating system. The LGPL is similar but allows your application to 'Link' to GPL code without having to adopt its license. MPL The BSD/MIT/Apache style licenses are some of the oldest and are sometime refered to as artistic licenese. They allow anyone to use the source code as they wish, with no requirement of providing modified code to the public. They merely protect the author from liability, and some require that derived works mention the use of their code. BSD unixes,Mac OSX core, some Microsoft networking librareis and the Apache web server use this license as well as many other core libraries.
Richard Stallman (RMS) Founded Free software movement (1983), Free software foundation (1985), created the GPL (1989) and GPL2 (1991). Wrote GNU emacs, the GNU C compiler and debugger (1987) which is the basis for almost every open source program and a vast amount of commercial applications as well. Considered the father of open source, one of the most brilliant software developer alive and an extreme right wing radical when it comes to software and freedom.
Eric S. Raymond Leader of the opensource movement, the author of "The Cathedral and the Bazaar", considered on of the most important literary works conserning software and freedom. The most vocal of the opensource leaders, many times at conflict with Persons, Stallman and Torvalds. Was recently the president of the open source initative.
Bruce Persons Open source advocate and co founder of the open source initiative and creator of the open source definition. Former leader of the Debian project, and all around voice of opensource. Considered much more moderate then Stallman.
Linux Torvalds Probably the best know figure head of the open source community. Created the Linux (Linus's Minix) kernel which spawned much of the open source movement we have today. He is sometimes refered to as the Benevolent Dictator, refereeing to his style of maintaining the direction and code patches submitted into the Linux kernel main source repository. Currently only about 2% of the current Linux kernel is written by Linus.
1. Displacing traditional software 1. MySQL ( goodby oracle,ibm, Microsoft) 2. APACHE (web server, java server, libraries) 3 SAMBA 4. Linux (workstations, servers, firewalls) 5. FireFox
2. but why 1. Cost is only part of the reason, small part 2. Darwinism of software means the qulity is better, freedom to use what works best with no lock in, freedom to tinker, tweak and customize. 3.Huge base of libraries and software, no re inventing the wheel. 4. If releasing open source code, you get thousands of eyes and community support.
3. drawbacks 1. integration and expertise costs 2. desktop software not ready for mainstream 3. Comercial support can be as expensive a propiartary alternative. 4. can be hard to point the finger. 5. can sometimes lack features (designed by and for engineers)