Linuxcnc - https://packages.debian.org/source/bookworm/linuxcnc
Large portions of the core code base are labeled as LGPL-2 - There is no such licence. It is either GPL-2 or LGPL-2.1
A bit of history:
Linuxcnc was forked from a National Institue of Standards & Technology project called the Enhanced Machine Control (EMC). https://www.nist.gov/publications/enhanced-machine-controller-architecture-overview
As part of the project NIST released code in to the public domain free from copyright or licence - This code base was then munged for the want of a better word by a few individuals outside of NIST and additional code added. The munged code had copyright & licence notices added without the consent of NIST.
Whilst public domain code can be used in a FOSS licenced project, without copyright (which by its very nature, public domain code is free from), any licence becomes unenforcable. There is also the moral question of taking public domain code and claiming copyright over it.
Would the experts of Debian-Legal care to comment ?