3rd reply to the same thread. Sorry, I am catching up on a ton of email...
My current MacPorts prefix is '/Volumes/blue/mp'. '/opt/local' doesn't exist on my system.
That reminds me of another issue we have with the way we currently add items to the PATH. Right now, we are (well, I am, since I coded that part) brutal and stupid: just add "common" locations to the PATH and do not even try to deal with user-specific configuration.
In you case that could mean that, even though you probably configured your shell to use /Volumes/blue/tmp, Inkscape does not know about it. I suspect (but would welcome confirmation) that if you set the PATH in environment.plist: http://developer.apple.com/mac/library/documentation/MacOSX/Conceptual/BPRun... it should work. As far as I know, this is the standard way of setting environment variables for GUI apps on OS X.
However, even if you use environment.plist, you still need to set the PATH in the shell. If I understand this issue well, this is because Terminal will first execute bash and the system level bashrc resets the PATH. So, to recapitulate, when Terminal starts, since it is an regular OS X app, it has PATH set (from environment.plist), then it executes bash, which sets PATH to /usr/bin:/usr/sbin and not much else, then bash reads the user configuration file and does the PATH modifications set there.
Since Inkscape is a GUI app that starts with a shell script, the situation might be confusing and this is where some testing would be welcome.
In addition, there has been some debate (notably in the MacPorts community) about using environment.plist: why set environment variables in the plist if the shell, which is where you are most likely to use them, does not even honor them? The second issue is that you might want to keep your newest versions of ruby, python etc. for custom shell level stuff and make sure you don't break any major GUI app and keep the default system versions for those. I personally disagree with that: when you install newer versions of some software, you generally want to use it.
So to sum up, if setting stuff in environment.plsit works for Inkscape, I would be for writing a FAQ about setting PATH in environment.plist and remove our PATH stuff from the bin/inkscape script. Removing it will cause people to ask about what changed and this should diffuse knowledge of environment.plist.
Then, if someone comes with a clever way of extracting the PATH modifications from the shell configuration file of the user, that would be a plus, and would make things more transparent. However, this is no easy task: BASH alone has many possible user level config files (.profile, .bashrc, .bash_profile and there might be others). And then there are the csh, ksh aficionados ;)
Please let me know what you think,
JiHO --- http://maururu.net