Gratis (adjective)

1. Given or done as a gift or without charge.
2. Something given or done without expecting payment in return.

Origin:

Late middle english: from latin, "as a favor", from gratus "pleasing".

Examples:

1. The concert was gratis for all the attendees.
2. The software was offered gratis to non-profit organizations.
3. The consultation was gratis for the first time customers.
4. The advice was gratis, he did not charge anything for it.
5. The meal was gratis, it was a complimentary dish from the chef.