I currently have telnetd running from the music partition, and no sync or fsck failed yet. Are there any verified incidents where that happened?

Yeah, I think so...

The first thread you mentioned isn't really related, but the second one got me on track:
Running an application from the music partition is not the problem, but the application in question must not have a file from the music partition open (which my telnetd hasn't) and its current working directory must not be on the music partition (my telnetd is running with cwd=/sbin IIRC). emptriv on the other hand probably keeps its trivia files open (which I think are stored with the binary) and
it is probably running with cwd=<path of emptriv>.
So what I need to implement is a way to install the software on one of the possible program partitions (hda2 or hda5) automatically if needed.

The only problem to decide on is wether I want to install all packages on one of the program partitions or to install only those that might interfere with sync/fsck. If I did the later, the package author would be required to indicate if the package might interfere with them.
It is probably easiest to just install all packages on the software partition(s).

Regarding the e2fs tools on win32: If they really where available and functioning reliably, that would certainly be interesting.

cu,
sven