Redmine

you need to find out what project id; query each and every table in redmine for that project id and save each entry id for each table you looked in; query each and every table that doesnt have project id with the appropriate key column(s) and save each entry for each table you looked in; export each saved entry from every single table; decide whether or not you want to keep the same id numbers from the original redmine (depends on if the other redmine has already used these id numbers); insert the entries into the other redmine; re-define auto-increment numbers per table as needed.

I think that will about get you there.

this is not an EASY task, if you aren't familiar with developing databases, you should probably not attempt this.

Than you for the reply James! I've came up with the same idea yesterday afternoon and started working on it. Exported all the queries that contained the project_id I was looking for, but nothing else. The following tables had project_id:
Documents
enabled_modules
invoices
issues
members
project_trackers
tine_entries
users
version
wiki

I've exported these in csv (reduced the number in users because I don't want to import that one, it is just good to know who was working on that project). It turned out I don't need to import these into a new redmine install. Maybe somebody will have to, but ATM I'm happy that I don't need to do it. :)

Thank you again James! :)

B.R.:
Bert