The creative commons license is described in theory and in the reality very different. In the theory, Creative commons licensed images and texts can be modified by anybody, which includes forking of an entire project. According to the theory, a user takes a creative commons photo, puts this in his own version control system, adds some additional colors to the photo and the resulting photo is used in the blog.
The surprising fact is, that this theoretical workflow can't be realized in the reality. The problem is, that Creative commons is not the same like free the content from copyright, but it will start a conflict between the original author of the photo and the user how has reused the image. What does that mean? Suppose the ininformed user has put the modified photo on his homepage. Then the original author will take a look at it and he will check carefully if the Creative commons license is fulfilled. In most cases, the author will come to the conclusion that the secondary user was not allowed to use the photo specifically in a commercial context. The result is conflict between both parties. So creative commons has not simplified the situation but it will produce new problems.
Let us define for which purpose Creative commons and the Gnu public license is a great choice. It's for the read-only mode. If a content is provided under a creative commons license, this will ensure that no paywall will protect the content. That means, CC-BY is equal to “the world has access for free”. What CC-BY and similar licenses (which includes the BSD license) are not solving is the problem of forking content. Which means, that the world is allow to take the content and use it for their own purpose.
The problem is not located in the license itself, but in the copyright law in general. Creating content which is more free than CC-BY-SA content can be realized with neural networks which are producing the content from scratch. Instead of copying existing information the idea is to use a generative grammar which will produce a new kind of work. This new content is not a derivative of the original work, but it's produced by a computer software.
What the user has to proof is, that his picture on his own website is a different picture which was licensed under the CC-BY license. If the pictures are different, then the copyright law is no longer valid. That means, the original author has as no control over the second picture. The second picture can be used for any purpose, which includes commercial applications, forks or whatever.
Basically spoken, CC-BY and the GPL license is protecting content which is the same. if picture1==picture2 then the CC-BY license can be applied. That means the author of picture1 can dictate the rules to the owner of picture2.
Let us describe the situation from a technical perspective. There is file on the harddrive called “image1.jpg”. The author of the file has tagged the file with a CC-BY 4.0 SA license and uploaded it to the internet. A second user uses the “wget /remote/image1.jpg” command to download the file. He opens the picture in the gimp software and puts his individual logo on the picture. The resulting image2.jpg is uploaded to the blog. Such a workflow will produce a lot of work for the lawyer. Even if the original picture was tagged with CC-BY 4.0 license and even if the blog of user2 has the same license (CC-BY 4.0) it's not clear if a copyright violation was there or not. In case of doubt it was a copyright violation. Not because of the CC-BY license but because image1.jpg and image2.jpg is the same.
The reason is, that a unix command like “cp or wget” is producing an exact copy. That means all the pixel information are the same. And pictures and texts as well are created by someone first. He owns the information no matter which license he has choosen for the content. The answer to the problem is, to replace the “cp” command by something which is not producing a copy but something else.
A very simple example for creating an image from scratch is to manual redraw the outline of the picture with a pencil. This is what artists are doing. They take a photograph as template, draw the lines with a pencil and then the colors are put into the drawing. The resulting image2.jpg has nothing in common with the original but it's an image created from scratch. That means, it's not important under which license the original content was licensed, but the image2.jpg can be licensed by the artists by himself.