In addition, the first two links I looked at that you claim do not require downloads actually do especially if you consider Flash to be a 1Click entry download. LOL!
I think most require Java, ActiveX and/or Flash for video viewing.
By the way, as netstairs pointed out (see link below), the Netstairs platforms including Hexa2 have superior and many more features IMO to those other companies.
However, the real point was that HEXA2 claims no downloads are needed. Not everyone will automatically update and the threat is there even when not using the web conferencing service. Additionally, hackers keep finding new ways to get in, so Adobe has had to constantly update with new versions.
Surely it would be better if HEXA2, Netstairs and the other Moradi web conferencing platforms didn't require a hacker-prone software to be loaded on a users computer.
Another problem with the AFP is that I don't believe it is supported on iPads or iPhones. It seems to be obsolete technology that Adobe is backing away from.