Have you done a search for MLTL software, I am surprised you didn't find any info.

Below is the first result I had in my browser, worth a read and maybe follow links at the bottom of the page.

Designing Mass-Loaded Transmission Line (MLTL) Speakers – Neurochrome

Maybe the multiway section wasn't the best place for this, as maybe the technique is more often used by the Single driver community?