For those interested on the subject:
Minidisk FAQ: minidisc.org Acording to this FAQ, RealPLayer, available on Linux, sems to be able to encode in ATRAC3, wich is one good new.
So we still have to find out how to write on the MD, but we can rely on other software for the encoding.
Id love to have a MinidiskEditor sitting on my Linux Box... :-)