Why does it have this exception at the end, if purpose is to protect author from being held liable?
The exception is so poorly written that it actually increases the risk of liability, thereby potentially defeating the purpose of the disclaimer.
It seems to me that what the drafter had in mind was something akin to this:
The licensor/author/contributor (what the disclaimer later calls "person" and which henceforth I call "contributor") may be held liable only if both of the following conditions are met:
- The final user or consumer used the work or product as intended, and
- the damage(s) stemmed from malicious intent or gross negligence on the contributor's part.
The second condition relates to, or at least is consistent with, the disclaimer statement that "[the] work is provided [...] without malicious intent or gross negligence". However, the exception should be more specific in that regard instead of only using the term "immediate fault", since "fault" may also consist of a state of mind which is less culpable than malicious intent or gross negligence.
The exception also should be clear about whose usage it means by the expression "using the work as intended". The likeliest, most reasonable interpretation is that the exception refers to usage by the final user. But, taken literally, the disclaimer is in terms of contributor's fault at the time of contributor's usage of the work as intended. The latter interpretation is not necessarily unreasonable, and special circumstances could arise so as to trigger the doctrine of contra proferentem.