Definitely looks like a parallel port DAC, with a potentiometer thrown in to control volume.

I have old pc with msdos: do these parallel dacs need drivers or I only need compatible software/games?

No need for separate drivers. There's a few games that support them. Support for these things is usually listed as "Covox" (Speech Thing) or Disney Sound Source. If a game supports these, there's a good chance it'll work with that device. A nice thing to try would be Inertia Player (a MOD player, one of the best IMHO). It has an option "Covox/DAC8 on printerport", which is a good bet.

Sounds like a shit (it sounds like early 80's arcade voice samples) but it works with it's original software and Intertia player (and other Covox compatible software I hope). But selecting disney sound source with games that supported it, all I can hear is static and garbled noise. Probably a low profile clone, it's called "Magic Sound" and I think it was only available in Spain and Italy (about 1995).

Yes, it looks like the typical resistor-based DAC, but I wonder about the batteries and the transistors. Are they part of some kind of amplifier?

yeah, it has got a knob (mark: 4KT 425M - Piher Spain) probably for volume control, but I tried it and it seems to change nothing, maybe it's broken. And sound quality is really awful, expecially speech, lot of background static noise (even with his bundle software).