Okay, here is how I got this to work in Slackware Linux...step-by-step:
Please note, run all these commands in a Linux terminal.
This should work, with slight variation, in any version of Linux.

Additional Required app
Alien for converting the novacom .deb to a Slackware package

Download alien .tgz package file from the link above and install it:
as root, installpkg alien-8.76-i486-1mch.tgz

From the head of this thread, download WebOSQuickInstall and novacom
Convert novacom with alien:
alien -t --noscripts palm-novacom_0.3-svn177284-hud9_i386.deb

Install novacom:
as root, installpkg palm-novacom-0.3-svn177284.tgz

Run novacom manually: <- (This was the magic that I needed to get it to work)
as root, /opt/Palm/novacom/novacomd (this is case sensitive)

Enable dev mode on the Pre:
In the Pre launcher screen, open the keyboard and type this:
upupdowndownleftrightleftrightbastart

This will bring up an icon for dev mode. Tap it, enable it, flick it away.
Plug the Pre into the USB port and choose "Just Charge the Battery"

Run WebOSQuickInstall as a non-root user:
java -jar WebOSQuickInstall.jar

In the program, under File...Options, select USB Device and check "Show Dev mode..."



Click Close

Click the plus sign to add the ipk files you want to install.



Select the files you want



Click Select, then Install

They will take just a few seconds, after which you can close WebOSQuickInstall and press control+C in the Linux terminal to end novacom.
Unplug the Pre from the USB and enjoy your new apps!