Cerulean Studios has announced that it’s making Trillian, the cross-platform social networking and instant messaging client, free for desktop and mobile users. Features previously restricted to Pro users, such as the ability to sign in from multiple locations, support for themes and activity history viewer, will now be available in free editions of the software, starting with Trillian 5 for Windows, which has just been released.

Other supported platforms, including Mac and mobile devices (iPhone, Android and Blackberry), will get these features added to the next updates when they’re released. For now, though, only Windows users get the full gamut of features with the release of version 5.

Trillian allows users to access multiple social networking and instant messaging platforms from a single application. It supports all major instant-messaging platforms, plus Facebook, Twitter and LinkedIn profiles too to give users access to their major networks from a single interface.

The major new feature opened up to all users is the ability to install the software on multiple devices and computers, and then sign in from different locations using a single Trillian user profile. Users can now also change the look of the Windows client via support for themes, while the activity history viewer allows users to search, review and bookmark past chats. There’s also the new continuous client feature, that allows you to seamlessly switch between devices in real time when chatting, allowing you to move between desktop and mobile device, and vice versa.

The existing Pro license has been changed to a new rolling subscription model, which will cost $12 per year. This removes all ads from the program, plus allows Trillian users to store all their chats in the cloud for backup and synchronisation purposes, which isn’t available to free account holders. Those who purchased Pro licenses for version 5 will be pleased to learn these will not be limited to 12 months, although upgrading to version 6 and future releases will require migrating to the new subscription model.

Trillian 5 for Windows is available for free download now, and requires a PC running Windows XP or later.