writingtoole/pdb reads and writes the PDB container (header, record list, AppInfo and SortInfo blocks) and has an lz77 subpackage that compresses and decompresses PalmDOC text records. It doesn’t interpret record contents: you parse the 16-byte PalmDOC record 0 yourself, which takes a few lines with encoding/binary. The code is small, stable and BSD-licensed, but hasn’t changed since 2019.
pdbwritingtoole/pdb is a Go package that reads and writes Palm Database (PDB) files, with PalmDOC LZ77 compression. How to extract text from a PalmDOC eBook.