What exactly is it that you need to do?
If it's just the data analysis operations, and you're comfortable with the command line, PLINK and some similar open source tools may provide what you need. PLINK 1.9, in particular, should be even faster and more memory-efficient than SNP & Variation Suite 8.
If it's the polished graphical user interface that you value, though, there is currently no open source alternative at the same quality level (you can try to use gPLINK, though). There are also some specific scenarios which might take another year or two to be well-supported by open source software, and you may be better off buying SVS8 if you need to handle them now.