It's possible to do it a dozen different ways. They can't license the technology because the technique is nearly 90 years old. It's one of those things that, within the industry, it's kind of surprising nobody has bothered with yet. All they're doing is throwing a graphic EQ between you and your headphones, which you can obviously do at home but is tricky to do on the road. The one thing they did that hasn't really been popularized is doing an audiology test to determine what your ELCs are, which is stupid easy, which is what their website does.

Of course, the website also plays back the "equalized" version at about 6dB louder, which automatically makes it sound better, which is pretty unfair but entirely within the parameters of marketing.

Sound quality actually matters a lot with podcasts. I listen 95% of the time to audiobooks at this point and speech intelligibility actually matters a fuckload. Music? Music can be whatever. Intelligibility takes a lot more effort. That's why the gold standard of "was the concert any good?" is "did you understand the lyrics."