I found in Google’s terms of service web page this:
5.3 You agree not to access (or attempt to access) any of the Services by any means other than through the interface that is provided by Google, unless you have been specifically allowed to do so in a separate agreement with Google. You specifically agree not to access (or attempt to access) any of the Services through any automated means (including use of scripts or web crawlers) and shall ensure that you comply with the instructions set out in any robots.txt file present on the Services.
And I wonder if I am violating this point by using DA. I haven’t checked the other search engines that DA connects to but they probably have something similar in their terms of service too.
Usually DEVONagent is only sending one request per search engine, that’s more or less identical and as automatic as using the toolbar search of Safari, Firefox etc. In addition, DEVONagent honors robots instructions unless disabled by the user.