Open Source Examples

Hi.

Do you know any OS projects which you would recommend if one asks for
some good architecture/programming/OO/... examples? Which are the most
representive ones?
I say OS since the code is accessable.

I really don't know: Are most of them quite good? Or just some? Or
does is depend (propably... I know)? Or can this not be found in OS
software by nature?

I just want to see some really professional developed software where
most agree that it is quite professional and may be regarded as a
reference example for good programming and designing
(architecturing?).

Cheers,
Robert

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