My guess is that SharePoint is configure to require authentication based on the HTTP Error: Status-Code: 401: Access denied.
You are going to need to determine the authentication method that your SharePoint site is using.
If it is set to basic authentication, you should be able to send the username and password in the soap header. If memory serves me right, think it looks something like this:
<soap:Header xmlns:share="http://schemas.microsoft.com/sharepoint/soap/">
< share:AUTHHEADER>
< share:USERNAME>Administrator</ share:USERNAME>
< share:PASSWORD>Password</ share:PASSWORD>
</ share:AUTHHEADER>
</soap:Header>
If it is set to forms mode authentication you are going to need to use the Login method in the Authentication.asmx web service to get your ASPXAUTH cookie.
This will be a challenge as you will need to include this cookie value in the request to the SOAP request header for the CreateMeeting method in the Meeting.asmx.
It doesn't appear that "com.niku.union.gel.SOAPTagLibrary” supports setting cookies.
You might want to try commons-jelly-tags-soap v1.0 which has a soap:invokeRaw method and might let you set the HTTP request headers to include the ASPXAUTH cookie.
V,r,
Gene