Google is your friend.
And no - apparently your beyond confused. What with the plethora of terms, systems and what not out there in the software universe - easy enough to do.
"Subversion (SVN) is a version control system initiated in 2000 by CollabNet Inc. It is used to maintain current and historical versions of files such as source code, web pages, and documentation. Its goal is to be a mostly-compatible successor to the widely used Concurrent Versions System (CVS)."
"TortoiseSVN is an easy to use SCM / source control software for Microsoft Windows and maybe the best standalone Subversion client there is. It is implemented as a Windows shell extension, which makes it integrate seamlessly into the Windows explorer. Since it's not an integration for a specific IDE you can use it with whatever development tools you like."
Now - there may well be some radio software out there that's maintained on an SVN system. But, TortoiseSVN, SVN or even CVS themselves have nothing directly to do with radio at all - let alone SDR or a Flex rig.
Now that's all just from my quick 30 seconds of googleing after enjoying a very nice lunch - if you've something else in minde that's also called TortoiseSVN - share!