Hi there! This is a good question. 🙂
For the most part, most TS2 creators are lenient about including their content/meshes in lot uploads. Especially since the game has already been around for so long, many creators are no longer active in the community and have since said that their creations are fileshare-friendly. I won’t lie and say I check the TOU of every creator of every object in my upload (I’m sorry if this is a bad habit, or lack thereof :|), but of course, if I’ve ever unknowingly redistributed something I wasn’t supposed to, I’d be more than happy to rectify that. (Off the top of my head, I can only think of a few CAS item creators who don’t permit redistribution of their meshes, but can’t recall encountering that for build/buy mode.)
As far as crediting goes, it’s not customary (at least, not as far as I’ve seen on tumblr) to provide credit for every item included in the download. The vast majority of us use the CleanInstaller to install lots and Sims, anyway, which provides a complete list of all the content included in the uploaded, which some people screenshot and post as credit. So I’ve occasionally seen it done that way.
Hope that helps! Have a nice day, anon. 🙂