bug#30571: URL vs Homepage in package headers

[Peter Oliver]

The Emacs Lisp manual at 
https://www.gnu.org/software/emacs/manual/html_node/elisp/Simple-Packages.html#Simple-Packages
 gives an example of a package library headers.  This example includes a URL 
line.  Later, the reader is directed to 
https://www.gnu.org/software/emacs/manual/html_node/elisp/Library-Headers.html#Library-Headers
 for more information about the available headers.  This second page makes no 
mention of the URL line, and instead describes a Homepage line.

Surveying the Emacs source code, it turns out that both URL and Homepage are 
used, although Homepage is more popular.

Should one of URL and Homepage be preferred to the other?  Are they aliases?  
Is one of these a typo?

--
Peter Oliver