This is the only definition of plagiarism that matters:
Common rule violations
These are the most common rule violations that newbies make. There are other rules than these.
- Plagiarism: If you copy some text from somewhere, then you should have a good reason for it, and you must link to the source. Doing otherwise is plagiarism. Changing a few words around doesn't matter. If we find that you plagiarized, then you absolutely will be permanently banned, even if we find it years after you did it.
Copied text from somewhere: check.
Has a good reason for it: check.
Link to the source: check.
Ergo, Ratimov did not commit plagiarism as defined by the admin of the forum. Any case to be made that Ratimov should still be punished should be based on evidence that other users have been banned for plagiarism even after including the source, which AFAIK has never happened.
Lauda and cryptohunter, on the other hand, both committed plagiarism according to these standards. It's pretty clear if you are able to set emotional judgment aside.