The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Panaram Ltd.:
The m-Call iPhone application from Panaram allows you to integrate your iPhone with your corporate or hosted phone system (PBX). Phone calls are routed through your PBX providing support for short code dialling, least cost routing and one number presentation. Supported PBX systems include BroadWorks, Avaya, Mitel and Asterisk.Advanced call back support is provided for BroadWorks and Asterisk users. What does this mean in practice? When a call is made using the m-Call iPhone application your PBX will make the call on your behalf and call you back (sometimes referred to as "Click to Dial"). To the person you are calling, it appears that the call comes from your office desk phone as they only ever see one number.With access to your iPhone contacts, m-Call also supports a favourites list as well as recent calls. For BroadWorks users, m-Call also allows you to control your common desk phone features such as Call Forward (always, when busy, no answer, unreachable), Caller ID Blocking and Do Not Disturb.For more information please contact your PBX administrator or service provider. Alternatively you can contact Panaram by emailing firstname.lastname@example.org.