Ok now what i found today..hope it will be helpfull
1.Copying Coppermine users to Wordpress via database problem is solved.
First check the database table design and be sure that primary key "ID" has auto increment selected.User name,pass and e-mail is enough to work with default value for other fields are ok.
2.Copying Coppermine users to PHPBB via database problem is solved.
Make sure that primary key "ID" has auto increment selected(mine is not).User name,pass and e-mail is enough to work,but you can select more fields like registration day or last visit.And always check your table for default values to see is that what you want.See phpbb administration for more.
My main problem with copying users are that.So checked the user tables for default values,and if your configuration for phpbb or wordpress needs a required field like e-mail be sure that copyed user has one for it.
And about the plug in;wpunited...
Poor supported plugin for phpbb.It looks easy but has some minor bugs.I've tested it on my localhost.Login to phpbb and then go to wordpress with a new page that plug-in created as blog.php.Yes it creates the user for wordpress when blog.php executed.You can define the role of user created when configuring the plugin.But one problem is when i go back to phpbb and try to log off it kicks me to the wordpress login screen
and keeps the user logged in.
My situation is installed coppermine first and the community growed and needed some new features.Then wordpress came and then phpbb.
My idea for basic solution is,copying all existing users to phpbb user tables via database.Then using that wpunited phpbb plugin to create all users in wordpress when they first visit the blog.And integrating coppermine with phpbb.Then linking all login buttons to phpbb login screen.
If i can manage that minor problem with wpunited,i think it will work and coppermine,phpbb and wordpress uses the same user tables.
I will post the further progress here soon.
Some help will come handy