Archive.org resource [*] ISO Mega Link v1.2.3.0 [*] BeatJam NetMD Drivers
Beatjam started as a separate piece of software but was adapted to add netmd functionality. The rabbit hole goes deep.
Beatjam (at least some versions) supports conversion from ATRAC to other formats [*], including in batch jobs.
At least one update can be found here [*], possibly a good source for others as well
News / Press Releases of features and versions of BeatJam:
https://av.watch.impress.co.jp/docs/20060116/dal219.htm [*] https://av.watch.impress.co.jp/docs/20051214/just.htm [*] https://av.watch.impress.co.jp/docs/20051207/just.htm [*] https://av.watch.impress.co.jp/docs/20050418/just.htm [*] https://av.watch.impress.co.jp/docs/20050405/just.htm [*] https://av.watch.impress.co.jp/docs/20010214/just.htm [*]