Until recently VCS has only been tested on Linux which, whith the GNU toolset, differs considerably from other UNIX-like OSes. These are some notes on the compatibility status.

The first and main target for compatibility is FreeBSD

• Worth a look: sedcheck (to check portability of sed syntax) http://lvogel.free.fr/sed.htm#sedcheck

Experimental compatibility introduced in 1.0.100a.

Compatibility modifications (from the Full changelog):

• Call bash through env ⇔ bash is not always in /bin/bash
• Ensure we're using the correct getopt version
• (1.0.100a) Try to use POSIX sed options when appropriate
  • (1.11) Use awk for complex regexes
• Replaced incompatible sed constructs
• Use mktemp's common GNU/BSD(/POSIX?) syntax
• (1.0.100a) Use jot instead of seq if required and available
  • (1.11) Replaced by awk

vcs works on FreeBSD 7.1-RELEASE but the output is still less refined than on Linux. See http://outlyer.net/2009-03-25:vcs-working-on-freebsd/.
The output on FreeBSD 8.0 matches the one on Linux so it might be some (minor) problem with ImageMagick's arguments.

Notes/References

• Mount ISOs: # mdconfig -a -t vnode -f file.iso. Only root can set up loopbacks?
  • Found in: Mounting dd dumped images as usual filesystems (also instructions for OpenBSD)