Especially powerful is the LCL (Lazarus component library) a GUI wrapper library which makes it possible to &quot;write once compile everywhere&quot; (Slogan of Lazarus).
An in difference to QT or gtk and such toolskits it looks native on every platform because in the backend LCL can use GTK, GTK2, QT, Win-API or in this case MUI to create the GUI, so the application look not like aliens but native.