All of the clones run on ODA libraries, including DRAFTSight, but ODA doesn’t have its own lisp engine, so each clone ships their own.
BricsCAD probably has the best lisp engine of any of the clones, though to be honest I’ve never tested all of them.
OpenCDL is an ARX module, both BricsCAD and ZwCad have ARX clones, which allows OpenDCL to be ported.
I do test many of the clones from a C++ perspective. All have very complete access to the drawing database, but none are complete as far as
Accessing the host Application and Editor, BricsCAD and ZwCad are probably the most complete.
for cheap, I like CMS Intellicad, tho it's missing features.
I’ve I had to choose a clone to do work on, I’d pick BricsCAD, ZwCad is a close second.
Also, for real drafting work, I absolutely must have a perpetual license.