I did not see Outside Source, but I would imagine Ofcom would accept that it was broadcast on a news channel not aimed at children, there was a warning (although it was late), BBC News was taking the programme live and was technically not in control of the feed which was being produced by the World News team and the topic of the item was racist attacks against police.
News may not be explicitly exempt but I have certainly seen swearing in the House of Commons not being apologised for, and that was during PMQ's.
EDIT: It appears that Outside Source is not on iPlayer and the BBC News schedule doesn't actually list it as being aired, which is interesting.
As regards "the most offensive language" (whatever that is, but we think it includes the F word), not aimed at children is only relevant to radio as there is no watershed on radio and the rules there are about whether children are particularly likely to be in audience. On free-to-air television however, it is irrelevant as the mere fact it is before the watershed is against the Ofcom Broadcasting Code as there is a complete ban on "the most offensive language" before the watershed:
Offensive language
1.14: The most offensive language must not be broadcast before the watershed (in the case of television), when children are particularly likely to be listening (in the case of radio), or when content is likely to be accessed by children (in the case of BBC ODPS).
There may be some latitude where programmes are broadcast live, as viewers may be aware of that fact and the broadcaster not able to prevent it. Ofcom may regard complaints as 'resolved', rather than finding them 'in breach', particularly if the broadcaster gave a full apology at the time of the broadcast. The fact a programme is live did not stop Ofcom upholding complaints against Live 8 concerts in 2006:
http://news.bbc.co.uk/1/hi/entertainment/4732712.stm Complaints about BBC programmes usually don't reach Ofcom these days as Ofcom requires complainants to complain to the BBC first and to exhaust the BBC's complaints process, unless there are exceptional circumstances. It doesn't matter if a broadcaster is not in control of a feed, as the responsibility for what is broadcast lies with them. The BBC World team should be aware of the BBC's own editorial standards. The issue here is about the uses of the F word not the N word.
As regards the swearing in the House of Commons, it may be that that was not "the most offensive language" and therefore didn't need an apology. The Speaker may also not have intervened for milder swearing as the F word is considered 'unparliamentary language' but some other words are allowed.
Regarding the I-Player, when programmes are on there, Ofcom normally expects the BBC to edit the instances out of the I-Player as well as having given an on-air apology at the time in order to 'resolve' the complaint. Or otherwise the BBC normally acts in this spoilsport manner, removing the very material we want to see, in order it seems to me to please Ofcom. On this occasion, the material was available on the I-Player for two hours rewind (on the live News Channel page) and was not edited out during that time.