The link isn't secure. It is HTTP not HTTPS and thus vulnerable to MITM.
The bitcoin addresses presented are static addresses. Many of these charities now have their own donation page, or a payment processor now.
That Sean's Outpost site is "Under construction". Is this list obsolete? These addresses might even be for a wallet that is no longer monitored or where the keys are still secure.
I would not recommend sending bitcoin to some bitcoin address on a third party website.
Here are the donation pages for organzations in that Bitcoin For Charity list (excluding Sean's Outpost, and Chicago Wish Foundation -- both of which are defunct):
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