Hi Pdelorme,
The Syncfusion.core dll is used to check for the license. Make sure that Syncfusion assemblies along with Syncfusion.core are deployed in the deployment machine.
Please have a look at the PDF file to deploy the web application.
http://www.syncfusion.com/Support/user/uploads/webdeploy_8b7da45e.pdfPlease let me know if you need any further assistance.
Regards,
Ramu