@Ejegg I should clarify:
There is a config variable $wgMFDonationUrl which can be false or a string.
If set to a string, a "Donate" button will appear at the bottom of the mobile interface for users in the mobile beta mode that links to this URL.
The URL cannot be customised in anyway. e.g. you can't pass the page title to the url.
The question is does the fundraising team have any plans on using this in the short term future?
Has this ever been enabled? If not, then I don't see a problem removing it. We may want to revisit adding a link at some point in the future, although my guess is the best place would be the sidebar menu.