They're hard to get hold of...
Pretty sure someone told me Toshiba had released another set though. I like the Toshiba ones. I've got 60. First set bought in 2010 perhaps...
I do all of the above KMS, WDS....PXE boot....
Edit: The only issue i have with licesning is i think they're sometimes not on long enough, so i do get the occasional "this is a non geniune version of windows blah blah"