Can DEVONthink store its database in a place other than Application Support, i.e., on an external disk?
Technically, yes. You can read about this in the DEVONthink Help file, under “How do I… / backup or move my data?”. If you are doing this sort of thing with DEVONthink PE, make sure you are careful not to replace your working database with an empty one, or replace a database with an older copy!
It’s easier to relocate databases with the upcoming DEVONthink Pro, which also allows multiple databases. DEVONthink Pro even makes it relatively easy to use a CD or DVD to host a database in read-only mode. Of course, performance would suffer, as these media aren’t as fast as your hard drive.
Also remember that if your database contains links to external files, those links can be broken, making the external files unavailable if your database moves to a different drive or computer.