is a free app for Mac OS 10.4+ that lets you easily organize your software license keys. The program has a sidebar showing the titles of all of the apps you add and a main screen showing detailed information like license key, software version, support contact information, date purchased, and the computer to which the license is assigned. You can also export a simple PDF of all of your software licenses (although the PDF has no column headings for some reason).
The Lizenzen .zip also comes with two other programs: a portable version of the software for taking your licenses with you on a USB drive, and grabbICON. grabbICON is included so that you can extract an app's icon to use for your software license entry in Lizenzen.
A word of caution: your license data is stored in an unencrypted text file.