>Is Qt really open-source, if so, why are they (trolltech) selling it?
Yes -- and no.
The X11 version of Qt is available under the GPL. ie: you use Qt without
paying for it, your app must be GPLd. Trolltech owns the copyright to Qt,
so they are able to relicense it in any fashion they see fit. This means
that they can (and do) sell a commercial license for Qt to anybody who
wishes to use it.
Note that the Windows and Mac OS X versions of Qt are *not* GPL.
Quote:>I mean, how do they motivate users to pay for what's free?
By letting those who pay for it use it in a fashion that is not
compatible with the GPL. It's basically saying, "We will give you
access to Qt at no cost, as long as you give access to your program's
code to the world at large. If you don't like that, we will give you
access to Qt for $BIGNUM, and let you use it without having to disclose
Trolltech can do this because, and *only* because, they hold the
copyrights to Qt. The GPL version is out there, and cannot be recalled,
but they are within their rights to relicense for those that persuade
them to do so (in this case, by paying out a sum of money.)
Quote:>Also, does Qt
>library really make a viable tool for multi-platform programming?
As long as you are prepared to pay for the Windows/Mac versions of
Qt, yes. If you aren't prepared to pay in this fashion, you can only
port your application to X11 systems (Linux, Solaris, HP-UX, AIX,
Irix, Darwin, etc.) unless you bother to port Qt to some other
Personally, I'd be happier if Trolltech released the Win/Mac versions
in the same way they have released the X11 version. However, as the
copyright owners, they are well and truly within their rights; and we
should be grateful for at least the X11 version. It's a very well
documented library; I'd argue that the documentation is more accessible
than gtk's. Pity about the choice of language, though (C++ is not my
language of choice - personal preference.)
"You didn't slay the dragon?!"
"It's on my to-do list, now come on!"