The download links themselves are fine, but they are being delivered in a manner called mixed content. Mixed content is when an encrypted HTTPS web site (forums.getpaint.net) tries to access a file from an unencrypted site that only supports HTTP (MadJik's site). Modern browsers may prevent this from happening by default, as a user visiting an HTTPS site may expect that all of their transactions are encrypted, as opposed to just some of them. As of September 2023, it looks like Firefox handles this with a warning and a prompt, whereas in Chrome the download attempt will just be silently ignored.
The solutions (which should work in all browsers):
A. You can actually still right-click the download, copy the link, paste it into your address bar manually, and press enter. It downloads normally (since it's no longer the encrypted forum that is sending you to the unencrypted file).
B. You should also be able to right-click the download link and select "save link as". The download process should begin, but then give you a warning message in the download manager that requires you to confirm that you're okay with downloading from an unencrypted site. It doesn't mean it has a virus or anything, just that you're downloading an unencrypted file from an encrypted forum.
C. There are settings you could theoretically fiddle with to disable this security feature on a per-site basis, but I think instructions on how to do that would be a bit beyond the scope of this comment.
