He means this:
Broadband is an “always on†internet connection that you can use as much as you like. However, many packages have set download limits or fair usage policies that determine the amount of data you can download in any one month. If you exceed this limit, your broadband provider may request that you either reduce your usage or upgrade to a more appropriate but more expensive, package. Some providers may CHARGE you, or in extreme circumstances, suspend your service if you continually exceed your limit.
Even if your package claims to be "unlimited" your ISP will probably have a fair usage policy that can still be used to impose limits.
For an example of what you can do with different allowances, a 1GB limit would allow you to download 20 MP3 tracks a month, whereas with a 15GB limit you could download 250 tracks a month.
What he is saying is the forum takes too much of his limit up.