In Swiss Ephemeris, we have an implementation of delta T which tries to be state of the art.

See documentation here
https://www.astro.com/swisseph/swephprg.htm#_Toc11319101

and source code here
https://www.astro.com/ftp/swisseph/src/

The delta T source code is in file swephlib.c
https://www.astro.com/ftp/swisseph/src/swephlib.c

The implementation is complicated by the fact that we try to be consistent with different versions of JPL ephemerides, which use different values for the Moon's tidal acceleration.

All the code of Swiss Ephemeris is published under GPL.

A commercial license is available for those who do keep their projects free of the obligations arising from Gnu public license,

For my products I use an algorithm (Meeus; Astronomical Algorithms 1998) to 'predict' deltaT into the future. Does anyone have a good source for a more recent algorithm that takes into account IERS values since 1998?