Regarding HLDS, there isn't one for OS X at this time, but listen servers work.
Though I should note that I have an unofficial version in the works. It's not quite ready and has a few issues, but it does more or less work as long as you have the Steam client is running. You can give it a try
here. You can just put the binary in the Half-Life install directory and run it from there. There's no HLTV yet, but it's on my todo list. I'm not exactly sure when I'll get back to it though, because I'm currently concentrating on a rewrite of
srcds_osx.