if we are allowed to use free for commercial use fonts in our designs can we use free for commercial use photos as reference material for illustrations? There are a lot of photos available under the creative commons license. I know we are not allowed to use free clip art as reference since we cant prove we own the copyright to it but we can't prove we own the copyright to a commercial use font so whats the difference?
We don't allow CC as reference for illustrations, because our ASA states that you must be the sole copyright owner of your reference material. There's also no way to guarantee the image itself is indeed public domain or CC.
As an example, what would you do if you used one image as reference, then 10 other people used the exact same image to create an illustration almost identical to yours? How can you claim copyright of your illustration? And, even worse, what happens if it turns out the original image was stolen from somewhere then tagged 'Creative Commons' on some file sharing site, and the original photographer and copyright owner starts seeing traces of their work being sold?
We do allow the use of fonts, but only if you've checked to make sure the font license allows for commercial usage in RF stock. But we don't allow someone to type in letters isolated on white: We ask that people incorporate the font into a composition or modify the font to create something unique.