To build wc3270, start a Cygwin shell, cd to the directory where the source code resides, and type:
make
This process will probably fail (sorry) because the Makefile assumes that you have installed a MinGW-compatible version of the OpenSSL library. This is not a commonly-available package but can be easily built from source. Visit the OpenSSL webpage for details.
To build without SSL support, there are three lines to comment out in the Makefile before running make.
wc3270 was developed primarily on 32-bit Windows XP, but should be buildable on Windows Server 2003 or Windows 2000. It has not been built or tested on 64-bit Windows or on Windows Vista.The source tarball also includes an .iss file for use with Inno Setup. This is used to construct the install executable. See the Inno Setup webpage for details.
To build wc3270wiz, unpack the wc3270wiz.tgz tarball into a directory on your machine, then use the Visual C++ File -> Open -> Project/Solution menu option to open the wc3270wiz.wcproj file. You can then use Visual C++ to inspect, modify and build the code.