Why can the author not be reached?

Well I can't, in fact.
And apparently noone I've been asking to can either.

I'd have been all the happier had I been able to ask him directly.
I just can't get in touch with him.
Can anyone ?

Have you tried contacting Vlad? (Developer of VDMSound). I'm sure he had to contact the developer of Sapucdex to include it with VDMSound.

Yes, I already did.

There's also an email address of him (SaPu's) hanging around, but no, didn't reply.
Oddly, didn't bounce back either.
Just fell flat.

Still I'd hoped I might luckily correspond with him in my/our mother tongue without needing to painstakingly translate each comma in English... 😅 but no avail 😢

O Sapucdex, my Sapucdex, where thou art, nobody knoweth nor substantially careth anymore :

I turned to wd for help and now Ye olde mystery of thee has been vanquished.

In fact I explained him the various sapucdex.c versions' mess that I was facing between 1.0.0.3 vs. 1.0.0.5 releases and the depressing outcome of my desultory attempts to work my way through.

Well, before I could add : Give me floccinaucinihilipilification or give me death !
he had already disassemblied things and divined before me what bug was there in the code that caused it to fail and
rewritten me a revamped version that I subsequently could compile and show to perfectly match the expected functionality of it (please note : in WinXP).

I'm expressing myself in a light-hearted mood, but folks I'm really impressed.
Kudos to wd for his skilfulness and warp+ speed helpfulness.
It's awkward to say it, but when you must you must
(I also understand he doesn't need my superlatives in the least, but I'm afraid he'll have to cope with them and accept 😜 ).

Now everyone has a working source among all the asm and C project files that can be downloaded together with VDMSound.

SaPu himself being ostensibly unreachable, I'd like to invite those involved in handling the latest VDMSound distribution to allow for the use of this substantial improvement in the source repository.
As I repeat, the 1.0.0.5 binaries thereof (exe and dll) were already sounding fine, it's the source that was broken/not up to date.

At this point in cosmic evolution, I'll try to retrace my way building on wd's new sapucdex.c as opposed to what I had before, in the hope of generating a Vista compliant refurbishment of this piece of software, if I ever can.
So far no good. But that's a different subject.

EDIT 2008-12-19:

finally found somehow a way to circumvent ioctl limitations dooming Sapucdex under Vista (thx wd for your help)
as this really is a general Vista subject, I guess I'll be going into it in the pc section/dgVoodoo pertaining thread.