Well, it's called "best of breed". It's the usual way to offer the best solutions available in an integrated manner.
In the case of nBBS, the forum software itself is our own code but when we find an open-source piece that can do something better than we already are, we are glad to study it and use it if it makes sense.
For instance, the BBCode parser is our own; I believe that it beats the pants off most other parsers out there.
Syntax highlighting as used in the admin control panel, on the other hand, comes from an excellent Javascript library. We prefer to focus on high-level features rather than reinventing the wheel.
BTW, I disabled the avatar resizing/de-transparency-ing, etc, as you can see in my avatar.
But I would like to point out that I just tested on an Invision 2.1 and it does the exact same kind of post-processing to my avatar. Why is it bad for nBBS to do this but OK for other forum software?