Your final AS coursework production must not feature any copyrighted material, but some of your vodcasts might. Below I consider some of the issues and considerations involved.
Since YouTube introduced an automatic detection system (see the Wiki) and signed deals with most of the major TV, film and music companies (as you'll have seen from your Media work, these tend to be subsidiaries of massive horizontally and vertically integrated conglomerates such as News Corp and NBC-Universal), the issue of 'fair usage' of copyrighted materials has evolved a little.
|Link at the end of the post: a very useful site for exploring the issue further|
|My vodcasts used clips short enough to be considered 'fair usage'|
I've tried to find a definitive acceptable length of film clips which won't generate a YouTube blocked upload, without success so far (if you find anything on this please pass it on). I'd suggest aiming for 30secs or less, using freeze frames with original audio removed for anything over this, but that's a guess. Check your uploads for anything being blocked. So far, we've not problems with any A2 music videos, just AS film vodcasts (and a compilation of scenes which used a Depeche Mode a couple of years ago), including one of mine (vodcast on scream queens + final girls, available to view on request) in which I simply used too much of Bride of Chucky.
FairUseTube.org provide a very considered analysis of the issues involved, YouTube's policies and also highlight some of the common abuses - where fraudulent companies simply claim you've used their copyright material when that's not the case. I think I may have found one such dubious claim on my channel, for past AS coursework where the soundtrack was composed in school using GarageBand! In such cases, the fraudulent company pockets the money from ads which YouTube force on to the upload.
See http://fairusetube.org/dvd-ripping-guide; http://fairusetube.org/youtube-copyfraud; http://fairusetube.org/guide-to-youtube-removals and other such links on the site.
YouTube itself offers a guide, including lengthy videos, though they shy away from being specific over such matters as how much of a single TV show, film or other text goes beyond the fair usage doctrine - see also the Wiki on Fair Usage.
The Uni of Houston's DigitalStoryTelling site also features a considered discussion of the issues and legal policies.