Where have you got this info from?
Real bogwood comes from peat bogs and over time a preservation process takes place that the wood won't actually rot for a very very long time (we're talking thousands of years and seriously doubt anyone is going to still have their aquarium running by then!) - and that is why it is so useful in dendrochronology. The preservation is actually fossilisation due to the acidic and anaerobic conditions in the peat bogs and is simialr to the way in which coal is formed (albeit over millions of years rather than the hundreds in whcih bogwood is formed).
Driftwood can be any wood, it isn't a type it just happens to be wood that has drifted ashore on the ocean. It could be fallen from trees, damaged buildings, discarded items, or from wrecks. And how could you be sure that it hadn't been treated with some chemical prior to becoming driftwood? It hasn't undergone the natural preservation process and depending on the type of wood, the quality, age, current state of decay, etc then it will at some point (maybe weeks, months, a year, maybe several years) start to break down within your aquarium.
Mopani grows in Southern Africa in shallow, badly draining soil with a high lime content (alkaline). It has a high oil content and is good a great many uses but again it hasn't undergone the natural preservation process that bogwood has and once dead (as I assume people aren't thinking of planting a live mopani tree in their aquarium) it will start to slowly rot and breakdown. It's safer than driftwood though and the breakdown is slow.
Any wood that isn't sufficiently preserved will start to rot when kept wet.
Although I suppose that didn't actually answer your question of where I got my info. Part of it is from general knowledge (I have a head full of odd abstract little pieces of info) part of it from researching what would be safe to put in my tank and good old Google searches
