Netboost is now hosted as a Bioconductor package. Please go to https://www.bioconductor.org/packages/release/bioc/html/netboost.html for the current stable release.
If you have any issues using the package then please get in touch with Pascal Schlosser (pascal.schlosser at uniklinik-freiburg.de). Bug reports etc are most welcome, we want the package to be easy to use for everyone!