Qt, the cross-platform C++ application development framework, turned 20 years old this week.

Currently maintained by The Qt Company, a subsidiary of Digia, the Qt framework’s first release of Qt 0.90 took place on May 20, 1995. The company is currently preparing for the impending release of Qt 5.5 in late June.

Lars Knoll, Qt’s chief architect and maintainer, reflected on his 18+ years with the framework in a blog post. He talked about why the project’s roots in both open-source and commercial software make it unique, as Qt is currently offered in four versions: Community, Indie Mobile, Professional and Enterprise.

“From the beginning, Qt has been released with both open-source and commercial licensing options,” wrote Knoll. “Over the years, we have worked on expanding this model, and, nowadays, Qt is actually developed as an open-source project. In this sense Qt is actually in a rather unique position, having a strong ecosystem with passionate people, as well as a commercial entity behind it, which backs up and funds most of the development.”

(Related: Digia gives Qt its own company)

The idea for Qt was born in 1990 by Norwegian co-creators Haavard Nord and Eirik Chambe-Eng, but didn’t ship its first public release until 1995. Qt began its development at Trolltech, which invested in building and extending the native application development technology and maintained the framework through its first four major versions up to Qt 4.0.

Nokia acquired Trolltech in 2008 and refocused much of Qt’s development toward mobile operating systems, while at the same developing more tools around the framework, such as the Qt Creator IDE and the Qt Quick GUI application module. Digia acquired the rights to Qt from Nokia in 2012, reverting the framework back to a user-licensing model and releasing Qt. 5.0 with a new modularized codebase supporting all modern mobile OSes. Digia spun the framework off into The Qt Company in 2014.

In an email to SD Times, Knoll said application development has changed a great deal over the past two decades, particularly around a more diverse selection of desktop, mobile and embedded OSes with touchscreens; introducing a new UI paradigm; and demanding more-robust APIs through frameworks such as Qt.