Ok, first two things:
- You could/should use the
equivs package to create a dummy package that provides
pulseaudio. This does that you don't have to install PulseAudio just to satisfy dependencies if you have solved compatibility otherwise.
- In this case though, the program seems to be working without any dependency problems (which technically is a problem in itself if it actually does not work without PulseAudio).
Some programs continue to use the ALSA system for sound, since PulseAudio has an emulation layer that catches these signals without any real issue. However, it is also possible, and Cockatrice seems to work this way from what you say, to use a specific PulseAudio driver directly to reduce complexity/latency/etc.
There is no "reverse emulation" available from what I know - no "PulseAudio->ALSA" mechanism on the software side ("ALSA" unfortunately is an ambiguous word since it provides both a hardware driver and a software audio handler; PulseAudio uses ALSA drivers to communicate with the hardware, but jams itself in between ALSA's software and hardware constituents).
All in all: no, if the program is written with PulseAudio exclusively in mind, I don't think there is a currently available way to turn the signals into ones that are understood by the ALSA software side. Perhaps it is possible to disable audio completely for Cockatrice, either at compilation time or at startup, to still be able to use it.
And a last option is to spend the time making PulseAudio work on your machine instead.