Just to clarify a couple of things:
1. We regularly point users to code snippets like http://pastebin.com/Hn0aQhUU which can help them integrate captacha with Events Manager without needing the Pro version of the plugin.
2. The Pro plugin helps finance the development of:
a) The free plugin, as well as the optional Pro add-on
b) The extensive (free) support for the free plugin given here on the WordPress forums
If you have a specific issue you'd like help with we'll try to assist.