Earlier quoted context omitted.
I think KHTML, as a part of KDE, was open from the start?
Sure it was, but how much additional effort did Apple put into the code base by way of WebKit? Apple didn't need to open source that work, even if the original was open source, and I'm sure the leg up made a big time-to-market difference for Chrome. Edit: Actually, KHTML is licensed LGPL, and that's a viral license if you make a derivative work. So I suppose Apple was forced to open source their changes when it final…
When LGPL code is linked with non-free code and the resulting work is distributed LGPL only requires that the changes to the LGPL code be open and that the object files for the non-free code are provided so that users can exercise their LGPL rights with regard to the LGPL portion of the work.
Apple could have separated out much of their work into separate files that contained no non-Apple code and that dynamically linked with the KHTML LGPL code and they could have kept those files closed. They would only have had to open the changes to the LGPL code.
If we accept the terminology that GPL is a viral license then LGPL is more of an immune system than a virus.