I've been getting mails, that this doesn't work anymore. 

Here's the explanation from Gerhard Jaeger:

  since sane-1.0.13, the "old" Plustek backend does no longer contain the
  parallel-port stuff. This all, including the code for the kernel-module has
  moved to the plustek_pp backend. This backend is able to control a
  Plustek parport scanner either by using the kernel module or from
  user-space using direct port I/O or the libieee1284 library.
  As mentioned, the plustek_pp source code, can also be compiled
  as kernel modul - the make file is buried at doc/plustek/Makefile.module.