Apologies if I sound like a broken record, as I've commented on other articles about remote desktop access. I've used FreeNX from http://freenx.berlios.de/ and have been quite satisfied. Performance is acceptable or better over lower bandwidth, higher latency links.
There've been no updates to FreeNX for over three years as its developer, Fabian Franz, and another major force in the effort, Kurt Pfeifle, have "moved on," as someone on the mailing list noted. There's a dormant github project Fabian put up after FreeNX's last significant development input:
Been a long time since I did any "research" on available software in this area because, when I need it, I've been using FreeNX. In a related development, NoMachine announced in December, 2010, that their next version, 4, would use a closed source protocol and implementation.