Cannot open project!
Please, see https://sourceforge.net/p/gerbv/bugs/211/
Please report it as bug.
Opacity (translation, rotation, scaling and mirroring) was added later. You can test it under Windows with  gerbv-win-static_20160713.zip. Copy init.scm file from 2.6.1 installation to the directory with gerbv.exe from the archive.  https://sourceforge.net/projects/gerbv/files/gerbv/gerbv-beta/
Confirming this on Windows XP 32 bits.
Remove code duplication
Accepted with changes as git e571679032812e526e48583f0d40190350ff757c
Allow to specify rotation together with translation.