Adobe non free code in type 1 fonts
The problem
Font hinting used to contain some proprietary code by Adobe, which was relicensed to Apache-2.0. That code is described here:
Black book page 97 available here (via archive.org)
There is also proprietary code by Adobe implementing routines for multiple master fonts. This was not relicensed.
How can I check
Lintian help see report here
Install the t1utils package and run the following command on the pfb file:
t1disasm file.pfb
Check if you see the non-free code.
If you only see the lines
{systemdict /internaldict known not
{pop 3}
{1183615869 systemdict /internaldict get exec
dup /startlock known
{/startlock get exec}
{dup /strtlck known
{/strtlck get exec}
{pop 3}
ifelse}
ifelse}
ifelse
} executeonly
] noaccess defYou may be on the good side, since this fragment and related fragments were created by Adobe but are now under Apache-2.0 license, brought to us via AFDKO (Adobe Font Development Kit for Opentype), see https://sources.debian.org/src/afdko/4.0.1%2Bdfsg1-2/c/shared/source/t1write in afdko packge.
Lintian is too aggressive here and complains about the above lines.
How to solve
Rewriting is difficult:
- the adobe code is part of the language
- some printers search and replace the adobe code by their own routine. Rewriting this code could crash your printer.
- the adobe code is buggy (leaks memory) and postscript interpreters patch it at run time. Modifying it could change the postscript interpreter behavior.