I found the terms for licensing the free edition here: http://www.manageengine.com/products/service-desk/licensing.html

This all looks good except for this paragraph: "Annual Subscription License: As part of your choosing annual subscription license, Zoho grants you a fee-bearing, nonexclusive, non-transferable, world-wide license to Use the Licensed Software including user documentation, updates and upgrades to which you are entitled as well as any plug-ins provided to you during the period of your subscription, provided that such access and Use of the Licensed Software is in accordance with the Single Installation License granted by Zoho. Under the Subscription License, the Licensed Software is licensed only for a subscription period of one year. You must renew your license at least 10 days before the expiry of the subscription period in order to continue using the Licensed Software. If you do not renew the license, you agree to stop using the Licensed Software after end of the subscription period and remove the Licensed Software from your systems" (Emphasis mine)

So do you mean that at the end of one year, in order to continue to use service desk plus you must purchase a license? Or is there a requirement to "renew" the free license every year? Seems like your offering service desk plus for free with the expectation of being able to start charging for the product after a year. While I'm not against paying for software, and admittedly service desk plus is a good product, I do have a problem with bait and switch "free" offers, which is what this seems like.