KISS (Keep It Simple, Stupid!) is a design philosophy that favors simplicity, solutions that are as simple as possible to achieve given task. This philosophy doesn't primarily stem from laziness and a want to save time (though these are valid reasons too), but mainly from the fact that higher complexity comes with increasingly negative effects such as the cost of development, cost of maintenance, greater probability of bugs (e.g. security vulnerabilities) and failure, more dependencies. This stance is related to technology minimalism.
Under dystopian capitalism simple technology, such as simple software, has at least one more advantage related to "intellectual property": a simple solution is less likely to step on a patent landmine because such a simple solution will either be hard to patent or as more obvious will have been discovered and patented sooner and the patent is more likely to already be expired. So in this sense KISS technology is legally safer.
Apparently the term KISS originated in the US Army plane engineering: the planes needed to be repairable by stupid soldiers with limited tools under field conditions.
Examples of KISS "solutions" include:
Compared to suckless, unix philosophy and LRS, KISS is a more general term and isn't tied to any specific group or movement, it doesn't imply any specifics but rather the general overall idea of simplicity being an advantage (less is more, worse is better, ...).
KISS Linux is an example of software developed under this philosophy and adapting the term itself.
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