Zoho Projects provides REST style Web APIs over HTTP.  With this API, users/developers can extend their web applications to push or pull data into or from Zoho Projects for application mashups. As the API is purely HTTP based, your application could be in any of the programming languages like Java, Python, ASP etc., to use the same.

The Zoho Projects API uses simple REST calls. All calls are POST requests to a URL of the form http://projects.zoho.com/portal/[portalname]/api/private/[format]/methodname?parameters

where,
methodname is one of the API methods.
parameters are query parameters passed as POST input.
format is one of the required output formats (xml/json)

All methods return an XML or JSON document whose top-level object is a <response> containing method-dependent information.

The users need to have an 'API Key' as well as a 'Ticket ID' for accessing the Zoho API. The API key will be used to track usage and the Ticket ID is required for authenticating the user for a particular Zoho service.