It's listed as between 10 and 15 volts on
this trigger voltage list with a "your call" verdict.
Personally I think it's highly unlikely it would hurt either camera, as the dangerous voltages on some flashes are quite a bit higher, some in the hundreds of volts, but it's still your risk. You might find
this thread instructive: Pentax DSLRs should be able to handle quite a bit higher than 15 volts, but if you find out otherwise, or if your sample of the Viv 2500 isn't internally the same model as the one measured for the list and actually triggers at 300 volts, then you're out of luck.
If you want a good inexpensive flash with a lot of control and a known safe trigger, I recommend scouting around for a Sunpak 383, typically in the $20-$50 range at auction.