I'm sorry, I don't know of anyone using Siebel. It should be pretty simple -- DotTwain does not use ActiveX -- instead it uses an IE hosted Winform Control. If you can do the following, it should work
1. Require IE -- this feature is only supported in IE
2. Get an OBJECT tag into the HTML -- that is how the control is inserted in the page
3. Deploy DotImage dlls, your control dll and our server license to the server
4. Get the .NET loading security settings on the client to allow .NET from your host
Manual instructions are here:
http://www.atalasoft.com/products/dottwain/demos/webdeploy/SecurityHowTo.aspx
But this can be automated with CASPOL
http://www.atalasoft.com/KB/Article.aspx?id=10216
Or you can use your ActiveDirectory to set it up for all users without doing anying on their machines (talk to your administrator)