a. Buying an original movie DVD gives you a licence to use it according to law; you still do not own the copyright in it. Generally, you may invite friends and family members to watch the DVD with you, if this does not amount to causing the movie to be seen in public. What amounts to causing the movie to be seen in public often depends on the facts. For example, if you only invite a select group of friends and relatives to your home to watch the movie, then it is less likely that you will be considered as causing the movie to be seen in public. On the other hand, if you invite a large group of friends and then permit those friends to invite their own friends to your home to watch the movie, then it is more likely that you will be considered as causing the movie to be seen in public. In such a situation, there is copyright infringement. A movie might be seen in public even on private property (e.g. gathering held in function room of a private condominium). b. Likewise, renting a movie DVD does not mean you own the copyright to it. You should read the terms and conditions of use that come with the movie DVD and ensure that your use falls within their scope. You may come across terms such as "For private domestic use only", which explicitly allow you to enjoy the movie privately in a domestic setting.In general, our copyright law recognises that the copyright owner, not the consumer, has the exclusive right to cause the movie to be seen in public. (Please see the answer to part (a) above for a discussion on what may amount to a movie being seen in public.)
All the above acts involve making copies of the copyright-protected music, songs, videos and movies. Hence, copyright will be infringed unless it is a situation of "fair dealing" as determined by the Court or if it is done for the purpose of criticism or review, which may be relevant in scenario (c) where opinions are often expressed. In the latter case, you need to make a sufficient acknowledgement of the work used. Further, if the copyright owner takes legal action against you, it is for the Court to decide whether on the evidence, you have genuinely uploaded the material for the purpose of criticism or review such that the exception applies.If the abovementioned exceptions do not apply, you should proceed only with consent from the copyright owners. This consent may be found in the terms and conditions accompanying your CDs/VCDs/DVDs. For example, some record companies expressly state the number of copies you can make of the music on other devices (e.g. personal computers, MP3 players). If the terms and conditions do not address your intended use of the music, songs, videos and movies, you may also contact the copyright owners directly for consent.