You should be able to do that, but it will take a minor modification to our code. In the /plugins/jlinkedprofiles/communitybuilder/communitybuilder.php file, at about line 341, you'll see:
$query = 'SELECT * FROM #__comprofiler_fields WHERE ( type = "predefined" AND name != "username" AND `table` = "#__comprofiler" ) OR type = "text" OR type = "textarea" OR type = "editorta" OR type="date"';
Update that to the below, which adds the -OR type="webaddress"- part at the end:
$query = 'SELECT * FROM #__comprofiler_fields WHERE ( type = "predefined" AND name != "username" AND `table` = "#__comprofiler" ) OR type = "text" OR type = "textarea" OR type = "editorta" OR type="date" OR type="webaddress"';
Once that's done, any web address fields should show up in the Field Mapping area of JLinked.
I've added a case to our tracker to include those types of fields in the next version as well.
Thanks,
Alex