Pro bono

(Latin) offered free of charge, provided at no cost (often refers to legal services)

Pro bono publico (often shortened to pro bono) is a phrase derived from Latin meaning "for the public good." The term is sometimes used to describe professional work undertaken voluntarily and without payment, as a public service. It is common in the legal profession and is increasingly seen in marketing, technology and strategy consulting firms. Unlike traditional volunteerism, pro bono service leverages the specific skills of professionals to provide services to those who are unable to afford them.
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Adjective
1. done for the public good without compensation
(similar) unpaid

Provided for free. Pro bono publico means for the public good. - (read more on Pro bono)