I am designing a race calendar and I need some good images. I have found some on stock sites, but they are for editorial use only. I know that most of these races have all runners sign a release of all photos taken. If I buy the photo, can I use it for commercial purposes without my own release? What if I take the photos at the race myself? The calender will not be sold, but will be used to advertise my website and the individual races.
A model release is a contract, a normal everyday contract, between two parties (usually the model and the photographer) - the fact someone (who is not you) signed a contract with someone else (who is also not you) does not grant you any rights what so ever.
It looks absurd if you try to apply the "but he signed a release with someone else" logic to other contractual transactions - if Alice sells a car to Bob that does not give you permission to drive it (but it was sold, just to someone else).
The release the model uses with the photographer is an agreement of the extent that the photographer may use the image(s). If you find this image on a stock site, that means that the model gave the photographer rights to post on the stock site.
There are limitations beyond this. If the image is for editorial use, that usually means the model does not authorize commercial use. This may often be done for self promotion purposes only. Writing an article on running? This runner? etc. You can use the image since it is editorial. Design a calendar, whether it's sold or used for advertisement, is commercial/marketing use and is prohibited.
You can take the pictures at the race yourself, but you will need permission from the event organizer and your own release of anyone recognizable in the image (in most countries).
There is so much misinformation on this subject...
People in or who are visible from a public place have no right to privacy, in any country. That's a myth. The law allows for a reasonable expectation of privacy only, there are legal protections against harassment and there may be restrictions on entry to events.
So if you are visibly wearing a silly hat through your bedroom window and I can see you from the street and I can take your picture with a normal lens then I can publish it editorially without any further permission from you or need to negotiate rights. If I were hiding up a tree with a 1800mm lens then that would be hiding and it would be reasonable that you would not expect to be seen and that might be considered an invasion of privacy.
What I cannot do is publish an image taken in a public place and imply a point of view or endorsement on your behalf. That's what the model release is for - if the image was used to advertise that you as the subject votes for the "Monster Raving Loony Party" and you don't then you're within your rights to sue the publisher for libel who in turn may sue me.
If I attended a private event with a perimiter where I need to pass security (for example) or access a normally private area then it depends on the terms of entry, if the organisers have not denied me the rights to sell my work (for example at the Olympics there was a specific clause covering it.) Then I could not use it at all - even editorially.
In the case outlined, if you were in a publically accessible place then so long as the other content doesn't imply in any way that those runners are endorsing you then you are good to go.
For those in the UK see this handy guide:- http://www.sirimo.co.uk/2009/05/14/uk-photographers-rights-v2/
Extra note re the original question: If you purchase an image without a release of a runner, but you know who they are then yes you can have them sign a release for you to use commercially if you wish. Although as I say, so long as you don't imply that they are promoting your services then you don't need one.