For those who are a little bored and want to understand how it works, read on. For everybody else, just ignore this post.
Macrovision is the older way of doing copy protection for analogue sources. Basically it messed with the "automatic gain control" by knocking off the sync at the top of the screen. This has not been implemented on the decoders so recording to VHS should never be a problem.
CGMS is the newer technology used for copy protection on digital sources. What it does is place a 'flag' in the VBI which is basically just the blank spaces after the last line of a frame. Pretty much every recording device is (as per international laws) designed to look for these flags. If the flag is there, it will not record. Some newer VHS machines actually support CGMS.
On a final note, (and as an interesting bit of useless info), there are two types of flags that can be set.
1. "CopyNoMore" - This flag tells the machine that this source may not be copied under any circumstances.
2. "CopyOnce" - This flag tells the machine that it is allowed to copy the source but once copied, it must replace the "CopyOnce" flags with "CopyNoMore" flags.
Obviously, if there are no flags, the machine knows it can copy as many times as it likes.