We are working on a web application which retrieves data using ODATA services and hence we do not require any CD license on our content delivery web application. We are looking for a possibility of using contextual image delivery engine to provide multi variant images for different devices where based on transformation url different images can be retrieved. Do we require cd license on our web application for using CID?
The installation documentation [Login required] seems to indicate that you need to first set up a normal Tridion CD Web application and install the transformation handler/servlet in that, which would imply that yes - you do need a CD license.
However, I have a feeling that there are not really any dependencies on Content Delivery, so you could try to give it a go without this (you may still need some of the 3rd party dependencies from Tridion CD however) and ignore any steps that are related to CD specific stuff. If this does work, like Nick points out, you should check with Support that this is allowed under the license agreement.
Another option is to run Contextual Image Delivery on the same servers that host your oData webservice. You don't have to host the transformation handler/servlet on the same server that serves the web pages, as it can transform images from any domain/URL - you just need to set up aliases in the cwd_engine_conf.xml file