"Treehouse" was also an concept of
Tad Williams' in his
Otherland series of books. The Treehouse idea was a sparsely connected series of
nodes on the '
Net' (Williams' high-tech
Virtual Reality version of
the Internet) which formed the basis for an
underground organisation of the same name.
It could be disassembled and rearranged regularly so as to avoid being stumbed upon by commercial operators or an inquisitive g-man. It was populated by hackers and retired programmers and while not necessarily a bad place, was frowned upon by commercial operators, in much the same way commercial monopolies like Microsoft view the Open Source Community.
In the Otherland series, the main characters must contact a hacker who resides in Treehouse to obtain access to the Otherland Network, a huge Virutual Reality network hidden from public view where technocrats planned to live for ever as gods. They need to access this network in order to rescue friends who are in comas that they suspect are the network's sentient operating system's fault.