Not only open source. Not only software.

Postel’s law

Be liberal in what you accept, and conservative in what you send.

Gall’s law

A complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch never works and cannot be patched up to make it work. You have to start over with a working simple system

Lindy’s law

The future life expectancy of some non-perishable things, like a technology or an idea, is proportional to their current age.

Cunningham’s law

The best way to get the right answer on the internet is not to ask a question; it’s to post the wrong answer.

Conway’s law

Any organization that designs a system (defined broadly) will produce a design whose structure is a copy of the organization’s communication structure.

Hyrum’s law

With a sufficient number of users of an API, it does not matter what you promise in the contract: all observable behaviors of your system will be depended on by somebody.