it would be great if instead of having their version of the zip, they could link to the TI Planet archive
That reminds me... I'll just say here that TI-Planet is reasonable enough to let people who
absolutely need a direct link, use our
download.php link (archive-id based, and which will make the user download the always-up-to-date file), and not necessarily the HTML download info page itself (even though the latter indeed provides useful information/metadata, like the license, screenshots, additional details, etc.). That said, it should be a requirement (basic decency?) to provide info such as author name(s), license info, etc, wherever the download is.
Too bad some other website(s) don't provide/want such an external download capability and restrict them to their own website.
("A word to the wise"...)
It's also noteworthy that TI-Planet tries to link directly to the original source
when possible (or at least wherever the author uploaded it himself), which makes sense when such websites provide a permalink system, otherwise, as soon as the link changes for whatever reason, downloads stop working, which is a big no-no for the end-user.
Recently, we've made it even clearer that some archives point to external sources, by effectively writing "ext" in the download button label, as well as the source domain in the info section.
We've also just added (yesterday, as of this post's date) a feature that will make the download fallback to a local backup of the file if the external source is down for some reason (but that requires us to make a local backup in the first place, it's not automatic; it will probable be done for important things only)
All that because the end-user must not have to face the consequences of having an unstable source host.