Some hints from my site:
Ich checked the last bridging file and tried to compare it with the last published file based on the phpBB 2.x bridge.
First at all, I have to say, that it was very difficult to compare the files and functionality, as some code was not really rewritten, but only reformated or moved. This makes comparison difficult, to unterstand, what has changed and additionally is makes it difficult to test and support this.
Secondary, most of the files are not running on IIS as the file format is not correct. Esp. the language files for german are corrupting an existing installation of phpBB, some pages are not shown anymore. Just open them in an Editor, if you see unformatted text, IIS will left the pages blank witch are using these files. Copying back the original phpBB files solves this. If they are correctly formatted, like all the other files in phpBB and coppermine, then they also will run on IIS.
The sql_files to update the database are not running as the auth_option_id field is an autoincrement field and you try to insert a blank value there.
Additionally, im not sure, if it is a good idea to change the default phpBB installation and database for the bridge. The bridge should not be a MOD, neither for phpBB nor for coppermine. It should work as it. If there is a need to add functionality to the bridge, it yould be work only with the bridgefile and the corresponding bridge table. Or it should be something optional. The result is, if you do not change the phpBB database, that you have no longer access to the coppermine gallery.
All other things I have dicovered, I will report later