@namespace (UserScript)
TampermonkeyやGreasemonkeyなどでUserScript (browser)を区別するために用いられるメタデータの一つ。
任意の文字列で良いが、意味のあるURLを使う人が多いね。
@name (UserScript)と合わせてスクリプトを一意に識別する。
The combination of namespace and name is the unique identifier for a Greasemonkey script. If a script is being installed, and a script with that same name and namespace already exists, it will be replaced by the new script. Otherwise, the new script is added to the set of installed scripts. A script author will usually put all of their scripts under one common namespace, and then assign each script a unique name. While the namespace is non-semantic, a URL is often used. Some authors use the common home page for the collection of scripts they have written. But remember, the namespace can be any unique value. https://wiki.greasespot.net/Metadata_Block#.40namespace