Phillipp, are you representing Alento's forum?
No, I am the original author of the UBB.classic => UBB.threads import script as well UBB Accelerator. I was just surprised how complicated it is to import a predecessor to a current UBB.threads installation.
I'm confused why you just interjected comments about the redirect script into a discussion about importing UBBCGI to UBB.threads...
I was talking about the redirection scripts that are included in the ubbclassic_6_7_import.zip. These redirection scripts are necessary to redirect any existing UBB.classic links to the new UBB.threads installation.
3:)Your version should have a accelerator php file that does use php., If you turned it on then it may attempt to run php and may crash if the new php version is not compatible..
This is a possibility. If UBB Accelerator worked previously in Ubuntu 14.04/PHP 5.5 then there might be an easy fix by removing line 55 from ultimatebb.php:
The function set_magic_quotes_runtime is no longer available in PHP 7 and cause a PHP Fatal error on never versions of PHP