The companies did not disclose the value of the deal, which analysts said was a fraction of the $150 million Nokia paid for Norway's Trolltech in 2008.
The software is used by some 450,000 developers for making applications for some 70 industries.
Up to 125 employees working on developing and licensing the software will move from Nokia to Digia, the companies said on Thursday.
Nokia bought the software through its acquisition of Trolltech and it was a central part of its strategy until 2011 when it decided to swap its own smartphone software for Microsoft's Windows Phone.
Digia said it planned to make Qt available for making applications for Apple's iOS platform, Google's Android and Microsoft Windows 8.
Copyright Thomson Reuters 2012
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