That was written for Slack-10.1
First get the source from
SourceForge and save it to ~/build/penguin-command/build/ or wherever you build Slackware packages.
Next untar it and issue "./configure -h" to see what options are available.
Then read ChangeLog, INSTALL and README (at the very least) to find out what the app requires.
Go to
Alien's SlackBuild Toolkit and build you a SlackBuild script and slack-desc file which you can put with the source.
If you want menu entries and icons checkout Eric's
file from the original and adapt for your SlackBuild.
That app looks pretty simple and Eric didn't even specify any ./configure options in the original script.
That's a quick down and dirty sloppy but will work for that app HOW-TO. Now I'll wait to get shot down in flames.