You may be speaking about the LiveCycle Data Express edition. If your application only uses LCDS 2.6 then the express fits the requirements that you describe. You can use that edition.
Be careful with the new versions of LiveCycle Data Services. The version 3 is a beta version available on labs. There is no Express edition for this beta and Adobe didn't announce any LCDS 3 Express edition. You have to wait the public availability of LCDS 3 to see if the business model changes.