Binuburan is actually the first stage in the process of making tapuy, the Northern Luzon wine made from rice. It is in the phase when the rice has just been inoculated with the fermenting culture and has yet to turn alcoholic. But it has been allowed to ferment for a few days, up to a week, so it tastes slightly caustic, like an over-ripe pineapple or grapes.
It is also the culture introduced to sugarcane juice when making basi, the wine of the Ilocos and Central Luzon regions that is based on sugarcane.
The bubur is made by mixing ground rice and pounded ginger with a small amount of a pre-made culture - the previous bubur - then fermented, molded, then dried under the sun.
Binuburan was actually exotic to me. That is saying a lot, because my life growing up in Pangasinan was full of what many citified folks would consider verging on the fear factor - consider snails, or frogs, or wild dwarf crabs. Fear factors extreme, actually.