As you know Switchfin is GPL licensed. We are using SVN repository to keep the source code.
If you would like to browse the repository please take a look at http://switchfin.svn.sourceforge.net/viewvc/switchfin/
In order to get the the source code you need to have SVN client. You can use text base SVN client or GUI based like TortoiseSVN
To get a copy of the trunk version of Switchfin you can execute

svn co http://svn.code.sf.net/p/switchfin/code/switchfin/trunk/ switchfin

If you need a release version you can execute something like this:

svn co http://svn.code.sf.net/p/switchfin/code/switchfin/tags/br4-ui2.15/ switchfin-ui2.15

If you have difficulties obtaining the code you can always ask in the Switchfin forum

Have fun!