All images held on flickr.com belong to the people that made the images, that is to say they hold the copyright. By placing their pictures on public display at flickr they are allowing anyone to view their images. It does not allow anyone including you to use that image in any way shape or form. And that is the end of the story for most images.
However, some users signify, via the Creative Commons license that anyone may use their images so long as they follow certain restrictions. All Creative Commons licenses require you to give credit to the person who owns the copyright. You are also required to indicate that the image is licensed under the Creative Commons license.
There are six different forms of the Creative Commons license and there are important restrictions that should be observed. Three of the Creative Commons licenses are for non-commercial use only. So if the website or printed material, or whatever it is, is for a company and not an individual or non-commercial organisation such as a charity, you are not allowed to use the image.
Another restriction on some of the Creative Commons licenses is that you are not allowed to make derivative works. Obviously by using it in some way it must be integrated into another “work” but internally you should not alter the image.
The final type of restriction is that if you do alter an image (one not covered by the above restriction) you must share any derivative work under the same Creative Commons license.
Those are the restrictions and the six variants of the license are
Attribution-ShareAlike License
Attribution-NonCommercial License
Attribution-NonCommercial-ShareAlike License
Attribution-NonCommercial-NoDerivs License
Keeping track of all the owner and license information for conform to the license is a lot of work. Lightboxr helps to make that work very easy by always keeping tabs on these details and allowing you to export all or any of it when you need it and for the photos you have selected.
Flickr has a page explaining the creative commons licenses if you want more informaiton.
Images without Licenses
As stated before, you should not use images that are not shared under the Creative Commons license. However, if you contact the owner of the image you are always free to negotiate whatever arrangement you want. Each image you see on this site shows the name of the owner in the form of a link to their profile page on flickr.com and there you will be able to make contact with them via flickr mail.
Etiquette, Politeness and Common Sense
The Creative Commons license does not require you to contact the person who has licensed the image. However there are a number of reasons why you might want to do so.
First, if someone has been kind enough to share their work for free, it seems only polite to send them a thank you note.
Second, if you are going to spend money using an image, like on printed material, it would be a shame to find the owner is not happy with your use of the image after your money is spent. It would be a really good idea to just let them know before your print run of 10,000 copies is done.
Third, images that contain pictures of people may require a “release” from the people in the picture which is a completely separate issue to the the copyright and may not be in the control of the owner of the image. Again the way you are using the image and the degree to which the person is identifiable can impact the legal position on the use. If you are spending money, check with the owner before you are committed financially.