Please download nwcc via its sourceforge download page.
Compilation is as simple as "tar xvzf nwcc_VERSION.tar.gz; cd nwcc_VERSION; ./configure; make; make install"
The following package managers include nwcc as well (note that some of these may carry outdated versions, so it may still be best to get the most up-to-date source archive from sourceforge instead):
As the number of supported platforms and correctly working features grows, it becomes more and more difficult to test changes and additions. So nwcc_VERSION.tar.gz is usually the last version that was tested on all supported platforms, and nwcc_unstable.tar.gz (if present in the current version branch) is the most up-to-date snapshot - which contains new fixes and additions, but may be broken in some unexpected ways on some platforms.
Note that some "second tier" platforms (such as MIPS - which hasn't been developed for in months) may not be tested for a particular release. They are then marked as untested in the version history table.