Is pine acceptable to build enclosure with?

There is nothing wrong with using pine, I've used it plenty of times myself for home built enclosures. If someone is telling you it's bad for your snakes, make them site references because quite frankly the 'volatile pine oils' explanation is a load of bull when discussing enclosures made from pine lumber.

used and built many cages with pine, I use bed liner paint ( inthe past ) to seal the inside and make water proof. (if you can find it still) makes sure you seal it outside. the stuff is strong and would allow 2-3 days to air out. I often put vent holes in the wood so the air does refresh itselh during the day.

completely safe. Pine is in most melamines composites too and they usually don't get the edges sealed at all. I would worry about melamine more than straight pine. Both have been used for years.

I would avoid most tropical hardwoods like cocobolo and such they can be quite toxic.