SQL & PL/SQL

In the company I work in, we've got some java applications working on two different instances which "hide" to each others (one on 10g and the other on 8i). Some decoding tables, which should common to both of them, are only present on 8i one.
I've been told that java works 'cause it allows to connect to both of databases and then report the information on front end applications.
The question is this: since we'll have to get reports on both of databases, is it possible to perform queries by using tools like oracle forms, oracle reports, sql developers, ... for joining the tables of the two different databases as java does? We have to get how to accede directly to the two instances for getting data from both of them for reporting activities. I remind you that we cannot use dblinks between the two databases for internal security reasons.
Thanks in advance!