Opera never stopped inventing new features and was (for me) the fastest browser especially on slower hardware, nevertheless, compared to IE and FF (there was no

Opera never stopped inventing new features and was (for me) the fastest browser especially on slower hardware, nevertheless, compared to IE and FF (there was no Chrome in these days). I remember the F9 quick configuration menu which allowed you to quickly turn on or off certain features, or the custom CSS bar to change the style of a website. Opera was also the first browser with a useful zoom function. One feature which was never adopted widely but was also quite useful were graphical tabs (today this is widespread in Windows and KDE for regular window previews). The list of opera features is kind of endless. It's such a pity this great browser was no further developed. I wonder why the developers did not open source the code/old engine in a way Netscape did it with Mozilla.