Are you aware of the phrase, "Free as in beer"? There are multiple definitions for the word free, one of which is like going to a place that hands you free stuff and you don't have to do anything to get it.

But when a prisoner is released, he is free. He now has freedom.

However, the prisoner may have to pay a nominal (or not-so-nominal) fee to be released. He may have to pay a bondsman to help get released. Or he may have to pay his debt to society for his freedom. Or maybe he gets released due to a technical or legal matter.

In any case, the freedom of a photo has two senses.

In the one sense, it can be free as in beer, meaning it has no restrictions or license fees. It is public domain. Old paintings can be reproduced this way for free.

However, a photo may also be free in a sense of freedom. It may be released on the cognizance of the licensee to use it in a narrow or broad range of ways. This is the case for royalty-free licensing. The licensor may tell the licensee that the photo can be used in perpetuity for any purpose as long as there is an attribution. No further royalties (fees) are to be exchanged, however there was an initial payment, like a bond, to set this photo into this kind of freedom.

So just like a prisoner may be set free after paying court costs or bonds or fines, the licensed photo can also be set free.

If I take a photo of an old painting, I can sell my photo, or copies of my photo. The use of the painting is free, but my photos of it probably are not.

And just like the former prisoner may have to return to the court/prison after a period of months or years, there are some licenses which expire. If a photo's license expires, it is supposed to be removed from circulation. This happens with film and other rights, too.

Free as in Freedom often has a cost associated with it.