I spent some time with l3enc in 2015 and confirmed that it still works (https://git.einval.com/cgi-bin/gitweb.cgi?p=abcde.git;a=commit;h=51dd63ab8779c20dc598d9e23180fe9048e683db) with the Linux CD ripper abcde, as well as publishing a web page to describe how to get it all working (https://www.andrews-corner.org/l3enc.html) on a modern Linux system. It works very nicely on Slackware -current :).
I approached Fraunhofer via email about buying an actual license for l3enc with no success, the person I dealt with had no knowledge or interest even of a 20 year old application, so on my own computer I have used a commonly available serial number. If this violates the rules here I hope a moderator will delete this post? Upon entering the serial number the file 'register.inf' is generated with the serial number written to this file.
However when run next l3enc ignores this serial number and demands it be entered again. Does anybody have an explanation for this? Both l3enc and register.inf are in the $PATH so I am a little puzzled by this or even how to diagnose the issue...
[...] However when run next l3enc ignores this serial number and demands it be entered again. Does anybody have an explanation for this? Both l3enc and register.inf are in the $PATH so I am a little puzzled by this or even how to diagnose the issue...
Never mind, I copied l3enc, l3dec and register.inf to /usr/local/bin instead of $HOME/bin and all was well :)
Have you considered trying the ripper called Fre:ac?
I mean, I can't imagine they'd want to sell you an encoder they stopped developing so long ago, especially now that MP3 licensing costs are a thing of the past.
Is the linux version as slow as the initial DOS version (0.97 or something) I've experimented with?
Admittedly, I ended up running it in FreeDOS in qemu, but on a Debian Buster system with a Core2Duo P9600 and 4 GB of RAM, it probably ran at something like 0.1x making a 320 kbps mp3.