Public goods are those that, once produced, cannot be limited in use to a chosen few while being characterized with increasing returns. In other words, the marginal production cost of such goods is strictly below their average production cost.
Open-source software is among the purest forms of public goods. DeFi, notwithstanding the ‘finance’ component, is essentially a form of open-source software where the codes and software are transparent for the public.
L2PAD, Uniswap, Metamask, and many other DeFi applications are all great examples of public goods.