Are you under the impression that rebuilding the whole thing on any of the popular development options currently available would result in lower maintenance cos

Are you under the impression that rebuilding the whole thing on any of the popular development options currently available would result in lower maintenance costs? Or a more open system? Let's say they rebuild it with a Ruby backend (or maybe Go? That's trendy these days), a bunch of React (or vue, or maybe whatever's current for Angular), Postgres (or MariaDB, maybe Oracle's MySQL, maybe even Mongo), maybe throw it on some Linux boxes with Apache. In 20 years that's all going to sound like "We built it on Notes and now pay $7500/month in maintenance and update costs" along with everything that'll happen in between when ECMAScript 10 deprecates a bunch of language features. Could it be better? Absolutely. Should the current system be kept and extended? Heck no. Is data migration a significant issue? Only in that it's a very complex system with a huge range of different types of structured data. They have programmatic access to the raw data, dumping it out is logistics.