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How can something be both commercial and non-commercial?

Trolltech does that with their Qt programming library.

If you use their libs to build a non-commercial and/or Open-Source project*, you pay them nothing, and they even give you a ton of goodies (and a sweet little IDE) with which to use their library code.

If you use Qt for a commercial and/or closed-source project (see also DAZ|Studio), you get to pay Trolltech ~$6k per seat in license fees, per platform (e.g. Windows, OSX, etc).

*(The OSS license you use has to conform to one already published at the OpenSource Initiative).

/P