Architecture refers to the design of a system, while infrastructure refers to the actual implementation of that system. The architecture for the Wikimedia Foundation's web servers is a specification describing how the servers are to be set up. The architecture specifies database servers running MySQL to hold the information, web servers running Apache and PHP to serve it and geographically distributed web cache servers running Squid to distribute the load. The infrastructure consists of the specific servers - mostly rack-mounted dual-processor AMD Opteron machines, software - mostly Fedora Linux, network connections and Mediawiki software. The specific hardware in the infrastructure could be replaced with, for example Intel Xeon powered servers, or UltraSPARC machines from Sun Microsystems without changing the architecture. The software could be replaced with Debian, Gentoo or Slackware Linux without changing the architecture.
Open source means that the source code for software is made available to anyone the executable software is, and that everyone has the right to modify and redistribute the software. Open source is different than the similar free software movement because it is based on technical, rather than political motivations. The underlying philosophy of the free software movement is that it is morally wrong to restrict access to source code or prohibit making changes to software. The open source movement is based on the idea that making code public improves its quality because a much larger number of people have the ability to find defects and improve the software. Linux author Linus Torvalds compares traditional proprietary software to witchcraft, where a few individuals have secret information that gives them an advantage over everyone else. Torvalds compares open source software to science, in which researchers share their results to allow for independent review of the results.
Bibliography
McNurlin B & Sprague R (2004). Information Systems Management in Practice (6th Ed.). Upper Saddle River, NJ: Prentice Hall
