jamesh, you are right, in that it is the NPL which is clearly a dual-licensors creation. The MPL only equates to that if Netscape used their right to change the MPL into the NPL or something similar. There is a difference between declared intent to make a profit off of proprietary versions (the NPL), and a loophole that would allow for this declaration in the future (the MPL). A loophole that exists for the FSF with the GPL as well, but in that case one would have to worry about leaning to the left rather than leaning to the right.

rendering libraries

You raise an interesting point with your reference to Mozilla's policy on non-original software. Someone ought to get in touch with the Mozilla SVG folks (any here?) and discuss this. I want my, I want my, I want my SVG (in Mozilla).

Wait, is libart specific to X11? That would be a more concrete reason why Mozilla can't standardize on it. I wonder if they've heard of Vector-AGG?

Hold it, what am I saying? The libart-enabled copy of Mozilla I have runs on Windows. Somebody has ported it. So back to my first question...

some time passes

Ok, here's the real answer to my question about libart and SVG:

From what I understand, SVG can't be added until all of the missing hackers (http://mozilla.org/MPL/missing.html) are found to complete the relicensing. If and when the are all found, Mozilla can include the LGPLed code needed to render SVG, such as Libart.