Emelia and Lola have created a new software application that allows messaging site subscribers to...

They can only sell this software through a not-for-profit company.

They can sell this software, but only if they make the software code available on a public server.

The software enters the public domain for free use and can be altered by other programmers, who must then make their changes freely available as well.

The software enters the public domain for free use, but any changes made in the future can be kept secret, allowing them to profitably sell the modified software.