[skeledrew]

It's not free if there's any kind of expected return.

[rightbyte]

If the return is also free, yes. A smile or a thank you is free to give.

[juliangmp]

Attribution would be one thing. See ooen-source and free software licenses.

[skeledrew]

There are specific constraints on "free" in that context. For example *GPL also generally forbids providing functionality without making the source available.