I am looking for some low cost or open source version control software that integrates with TDP.
I don’t think you’ll find anything that will integrate directly into TDP, but from what I can tell all of TDP’s files - snippets, configs, automations, etc. are all XML files, so any version control that handles text well (Git, SVN, Mecurial, etc.) should be workable.
Personally I use a GUI for Git call SourceTree to manage a local repository that I synch occasionally with a network based one for my snippets, etc.