What is a) from 2. Granting of rights of use ?

[666fa58935b35Roarkes]

2. Granting of rights of use

   a) By creating a contribution, you give the operator a simple right to use and modify your contribution within the framework of the forum, which is unlimited in terms of time and place and free of charge.

It is to modify a error made by a user in a topic or use and modify a mod made by a user ?

[666fa58935f0aKolya]

We have done both in the past, usually on mod posts.
We may insert tags into a mod post, modify installation instructions as technical demands change, add screenshots, etc. We have also in some cases modified mods for similar reasons, eg the most downloaded mod on this site - Cyberblutch Rebirth models - was first complemented by me with resources Cyberblutch had created but not included, then updated several times by voodoo for use with NewDark and other mods. ADaoB evolved into SCP. I think most of the big ones are the work of multiple generations of modders by now.
If the creator is still around we always ask them to make changes themselves or offer our help. But over the years a lot of creators have left the scene, and then we've taken the liberty to update their mods on their behalf.

So the terms of service refer to all contributions. It's a legal description of what we've been practising all along. But if you want to know the reason this clause exists (as it did in the previous version of TOS): Over the years there have been some users (3 or 4) who demanded we delete all their posts when they decided to leave the forum. I always rejected that demand, because it would disrupt the conversational flow of those threads.
After the first one threatened with legal action if we didn't delete his posts, I remembered reading a similar clause in TTLG's TOS a few years earlier. And then I understood why they had it and why we should have it.

[666fa5893602aRoarkes]

Thank you for the answer.