OpenVSP should run on Windows without installation. Simply unzip the archive to the location of your choosing and double click vsp.exe.
If OpenVSP does not work on your installation, please report your problems to the mailing list.
Compiling OpenVSP on Windows is a fairly involved process. Rudimentary instructions are provided in the README distributed with the source, but a more detailed set of instructions have been made available for download in PDF form here.
OpenVSP requires libjpeg to be installed on the computer. A ready-to-go DMG for the libjpeg library is available here.
Once libjpeg is installed, unzip the archive to the location of your choosing and run the vsp executable.
There are no pre-compiled Linux binaries produced at this time. In order to run OpenVSP on Linux, you must compile it yourself.
OpenVSP is available from the FreeBSD's port collection. Installation instructions:
$ cd /usr/ports/cad/openvsp (as root)
$ make install
$ portinstall openvsp (as root)
This will pull all the dependencies needed to compile OpenVSP. Then it will automatically fetch, compile and install OpenVSP in your system.