You didn't say specifically what code you are updating. If you are updating one of the codes from SCALE 5.0 or 5.1, you must be a licensed user of that version of SCALE. Each version is licensed separately. A license for SCALE 6.x does not mean that you can have access to an earlier version such as SCALE 5.x without a separate license.
If you have a license for the version of SCALE that includes the code you are updating, but you have lost the documentation, you might be able to request a PDF file of the documentation from RSICC. The code documents for earlier versions of SCALE were export controlled and could be given only to those persons who had been approved by RSICC and who had signed the license agreement. The documentation was not freely available to others, and in fact sharing it would be a violation of the license agreement. The code documents for the newest versions no longer contain certain details of the implementation (much to the consternation of those of us who like to understand the inner workings of the code without spending hours figuring it out) and are no longer export controlled.
If you are working on updating a version of one of the codes in SCALE 5.0 or 5.1 and you are not a licensed user of that version, you and the person who gave you access to the code are already in violation of the license agreement.