Ok, I found a workaround...
Since one database was allowing me to see views in the mapper, I simply created the view in that database as a trivial "select * from otherdatabase.view", added this new view to the mapper and saved the updated model.
Then I opened the .ORM file, changed the datasource to point to the correct database, saved it, re-opened the mapper and forced it to regenerate the model.
Finally, I deleted the temporary view in the database and everything appears to be working, so far.
The views are still not showing up in the Object Mapper, but at least the code generator doesn't seem to care, so I am able to create a class from the database view.