Synergy isn't open source.
My 2 cents anyway:
Pricing is reasonable for this kind of thing. The built-in tutorials are a nice touch.
It's complex to use but, well........it does complex tasks.
User forums are non-existent afaik.
Ask for a key and you'll have a fully functioning 30 day demo with no annoying follow-up calls from salesmen. At least that was my experience.