BlackBerry has fulfilled its promise by releasing BBM for Windows Phone. But don't get too excited, because most of you can't use it straightaway.

BBM - also known as BlackBerry Messenger - is a messaging client included on BlackBerry devices. It allows people to chat and place video calls, among other things. BlackBerry released the service as an app for Android and iOS devices last year, and it said BBM would also eventually release for Lumia handsets. The exact date was never revealed however, with BlackBerry only committing to a broad time scale between May and July.

On 8 July, BlackBerry launched a beta version of BBM in the Windows Phone Store. It's a private beta, meaning you can only begin testing the service after you've received an invitation directly from BlackBerry. PhoneArena noted that it shouldn't take very long for the company to open BBM to all Windows Phone users. After all, BBM has more than 80 million monthly users - and BlackBerry views the service as a crucial asset to the company portfolio.

John Chen, the chief executive at BlackBerry, told analysts last year, for instance, that BlackBerry might even consider charging users on a monthly rate, or something similar, as long as enterprise users adopted BBM as a messaging client. With Facebook buying messaging apps like WhatsApp for $19 billion, Chen has clearly realised that BlackBerry is sitting on a potential cash cow.

READ: BBM finally coming to Windows Phone in July

But for now, BlackBerry still needs to work on boosting BBM's monthly active user numbers. It's therefore pushing out the BBM for Windows beta and getting ready to welcome Windows Phone users to the BBM community.