AnywhereTS (http://en.wikipedia.org/wiki/AnywhereTS) is a terminal services client (for Windows platforms) which are used by approx 350,000 people worldwide. They have gone out of business and are opensourcing their source code - it is possible that they have support for RDP 5.2 and that code can be leveraged in remote desktop.
their forum for requesting access is http://anywherets.com/board/viewforum.php?f=10&sid=9bb9be45749fb3067424fc0b9a973e3e
Their front page announcement is http://anywherets.com/. Note that their website will go down as soon as their hosting contract is up.