PsychoPy

Pygame   (Compare Project)

Mostly written in Python

License: lgpl

Crazy Eddie's GUI System   (Compare Project)

License: mit

Thousand Parsec KDE Client   (Compare Project)

Mostly written in C++

License: gpl3_or_later, lgpl

Qt 5   (Compare Project)

Mostly written in C++

License: Commercial, GNU_Free_Documentation_License, gpl3, lgpl21

OpenTK   (Compare Project)

Mostly written in C#

License: mit

Agar   (Compare Project)

Mostly written in C

License: bsd

Seed Framework   (Compare Project)

Mostly written in C

License: lgpl3

Illarion   (Compare Project)

Mostly written in Java

License: AGPL3_or_later, Proprietary

Elysion Framework   (Compare Project)

Mostly written in Pascal

License: mit, mozilla_public_1_1

Clutter Toolkit   (Compare Project)

Mostly written in C

License: lgpl21_or_later