I installed the most recent version of Tea Commerce a few days ago and developed the add to cart function for my products (based on the sample site) over the weekend. I am sure that this part of the code has not changed but I am now getting the following error in the browser when 'Add to Cart' is clicked:

Cart Error: 
<error><![CDATA[MESSAGE:
Exception has been thrown by the target of an invocation.
STACKTRACE:
   at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at TeaCommerce.Presentation.TeaCommerceBase.RequestModule.invokeMethod(restExtension myExtension, Object[] paras)
INNEREXCEPTION:
System.IO.FileNotFoundException: Could not load file or assembly 'Umbraco.Licensing, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. The system cannot find the file specified.
File name: 'Umbraco.Licensing, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null'
   at TeaCommerce.Licensing.ALicenseValidator.Initialize()
   at TeaCommerce.Data.Licensing.LicenseValidator.get_Instance()
   at TeaCommerce.Data.Order.Save()
   at TeaCommerce.SessionController.get_CurrentOrder()
   at TeaCommerce.SessionController.CheckCurrentOrderPaymentStatus()
   at TeaCommerce.Base.AddOrderLine(Int32 nodeId, Nullable`1 orderLineId, Decimal quantity, Boolean isUnique)
   at TeaCommerce.Base.AddOrderLine(Int32 nodeId, Decimal quantity)
WRN: Assembly binding logging is turned OFF.
To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1.
Note: There is some performance penalty associated with assembly bind failure logging.
To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog].
]]></error>

It looks to me like a licensing problem, which is understandable as I have not added one yet, but I thought that Tea Commerce could be used without a license up to a certain number of orders:

"You can download and test all Tea Commerce features for free, so you know what you're buying before you pay for it. The free version is limited to 10 orders, but these can be removed to allow more development/testing."

Any ideas please?