This has been one of my biggest peeves about the WWW since 1993. Please include publication and/or change dates and/or include a changelog on your pages. Do not force your users to resort to reading metadata, the URL path, the Wayback Machine, or dark magic to figure out when and what changed. Diff is a solved problem; why can't I diff a generic web page?
The only thing to which you are entitled–by definition–is access to the source. It is your responsibility to verify what the source does.
The "getting paid" notion is off-topic and has nothing to do with the source being open. If I provide commercial support for someone and implement a solution using open source software, I am the one providing the support and I have no expectation that the original authors will hold my hand.