The essential parts of a trade secret are that (a) it is something that you keep secret, and (b) something that gives you an advantage in trade because you know it and others don't.
A trade secret remains a trade secret if you give it to someone else under a non-disclosure agreement. If it is available where anyone can download it, either intentionally or by carelessness, then it isn't a trade secret anymore (as soon as it actually gets downloaded).
If it gets made public through some illegal activity, well, that's too complicated for me.
Anyway, YOU don't have to pretend anything. A claim that something is a trade secret doesn't make it one. And if something is a trade secret, no claim about it is necessary. If you download the software without doing anything illegal then it isn't a trade secret.
To reply to the comment: If the sequence of events is this: I download the source code. I read the license. The license says "by using the software ..." then clearly I have the source code before using the software. At that point the trade secret status is lost. We don't need to discuss whether the license would have been enforcible, because the software is already downloaded before the license starts applying. I can tell anyone in the world about it. (I can't give the software to anyone, because that is copyright infringement, a totally different matter).