Well, a quick Google API search LiveMeeting opens this link .
In particular, it looks like they are all XML based, so you can call it with Java. Below is the closest to sending the invitation I could find.
Create a meeting requesting invitation text for an audience InviteText / presenterInviteText in the field list
API Live Meeting . , CreateMeetingReply. , API. - , Live Meeting Manager .
, InviteText FieldList. XML- -.
InviteText presenterInviteText FieldList createMeeting, . , , , / .
<PlaceWareConfCenter authUser="apiuser" authPassword="Pa$$w0rd">
<CreateMeetingRequest name="status" title="Tailspin Toys Status Meeting" maxUsers="25">
<OptionList>
<TimeOption name="startTime" value="2006-12-01T18:00:00Z" />
<DecimalOption name="duration" value="1800" />
<StringOption name="audiencePassword" value="auPa$$w0rd" />
<StringOption name="presenterPassword" value="prPa$$w0rd" />
</OptionList>
<FieldList>
<Name>audienceInviteText</Name>
<Name>presenterInviteText</Name>
</FieldList>
</CreateMeetingRequest>
</PlaceWareConfCenter>
XML.
<PlaceWareConfCenter>
<CreateMeetingReply>
<MeetingReply>
<OptionList>
<StringOption value="Jeff Hay has invited you to attend an online meeting using
Microsoft Office Live Meeting.

https://www.livemeeting.com/cc/contoso/join?id=name10&role=attend&pw=auPa%24%24w0rd



AUDIO INFORMATION
Audio has not been set up for this meeting.


FIRST-TIME USERS
To save time before the meeting, check your system to make sure it is
ready to use Microsoft Office Live Meeting. 
 http://go.microsoft.com/fwlink/?linkid=52354

TROUBLESHOOTING 
Unable to join the meeting? Follow these steps:
 1. Copy this address and paste it into your Web browser:
 https://www.livemeeting.com/cc/contoso/join
 2. Copy and paste the required information:
 Meeting ID: name10
 Entry Code: auPa$$w0rd
 Location: https://www.livemeeting.com/cc/contoso/join
If you still cannot enter the meeting, contact support:
http://r.office.microsoft.com/r/rlidLiveMeeting?p1=7&p2=en_US&p3=LMInfo&p4=support" name="audienceInviteText">
</StringOption>
<StringOption value="Jeff Hay has invited you to present an online meeting using
Microsoft Office Live Meeting.

 https://www.livemeeting.com/cc/contoso/xmlapi6/join?id=name10&role=present&pw=prPa%24%24w0rd



AUDIO INFORMATION
Audio has not been set up for this meeting.


FIRST-TIME USERS
To save time before the meeting, check your system to make sure it is
ready to use Microsoft Office Live Meeting. 
 http://go.microsoft.com/fwlink/?linkid=52354

TROUBLESHOOTING 
Unable to join the meeting? Follow these steps:
 1. Copy this address and paste it into your Web browser:
 https://www.livemeeting.com/cc/contoso/join
 2. Copy and paste the required information:
 Meeting ID: name10
 Entry Code: prPa$$w0rd
 Location: https://www.livemeeting.com/cc/contoso/join
If you still cannot enter the meeting, contact support:
http://r.office.microsoft.com/r/rlidLiveMeeting?p1=7&p2=en_US&p3=LMInfo&p4=support" name="presenterInviteText">
</StringOption>
</OptionList>
</MeetingReply>
</CreateMeetingReply>
</PlaceWareConfCenter>