ICD itself is only released by the WHO under certain conditions, which means that the classification is not publicly available as such. However, you can get it anyway from http://www.who.int/classifications/icd/en/ by reading through their contract. In a nutshell: as long as you do not monetize it, you just create a user account at WHO, agree to the terms and conditions, and then download the classification data in ClaML or plain text files.
Both files are not going to help you very much with using an OWL API though, but you might find that parsing the plain text files will be very easy. For example, a line in the code description file looks like this: