Can you contact them and ask when a Yosemite compatible version is coming out? You paid for it, so there is some expectation of service and maintenance.
I did. Here was the response:
Thanks for reporting this. It seems like Safari in Yosemite behaves in a strange way. Instead of the Safari process being identified as Safari, it changes its identifier to the site youre currently browsing. Other browsers and previous versions of Safari simply identified themselves as expected.
When you allow an app in Spark Plug, the app itself and anything launched by it will be allowed network access. Here, it seems like Safari doesnt launch an extra process called, for example,
http://www.google.com, but instead renames itself to
http://www.google.com. As such, Safari is unfortunately incompatible with Spark Plug on Yosemite.
Im very sorry.
Juuso Salonen
Private Eye