Scott said: one more thing: debian is discussion dropping libdb (the db the node, but not the wallet, uses). That might force our hand as well: either ship and support upstream's included libdb or drop the node and just ship the wallet. libdb long-term security maintenance might be challenging.
------------------------------ Actually, it's the other way around. Since version 0.8, BDB is *only* used for the wallet, not anything else. IIRC it was also used by the node component until 0.8, where it was replaced with LevelDB. In fact, if you configure with --disable-wallet, BDB isn't needed at all. But yes, as someone mentioned, BDB is not backwards compatible. If you've been shipping with any version newer than 4.8 (which is not recommended and throws a a warning when configuring for this reason) you need to take responsibility for ensuring that that version or newer remains available.