The weblib.pl bit is probably not the right path; that changes the HTML form (and I think only the quickupdate form at that), and it sounds like the information is coming in from the original form correctly. It's just getting lost somewhere between post and crosspost.
The crossposter actually loads the original post locally, then pulls all of the information from it into an XML-RPC request. That request is then sent directly to the remote server, which then processes that request and makes a new post there. Since we know that the local post is working correctly, the problem is likely happening either when creating the XML-RPC request (locally), or when handling the XML-RPC request (on the remote server), or possibly even in transport somewhere.
If I were working on this, I'd do the following:
1) Set up an account to crosspost from my 'hack to a second account on my 'hack (use 'other site' for the site, and for the URL use http://your-site-name/interface/xmlrpc). That way I could see what's happening on both sides of the post.
2) Add in some debug code in cgi-bin/DW/External/XPostProtocol/LJXMLRPC.pm to show the value that's being put in for the taglist there.
3) Add in some debug code in cgi-bin/ljprotocol.pl to show what is being received as the taglist property on crosspost.
Then go from there.
(Oh, and debug code in LJXMLRPC.pm will appear in the output of bin/worker/xpost.pl; debug code in ljprotocol.pl should appear in your Apache log.)
hmmmm
The crossposter actually loads the original post locally, then pulls all of the information from it into an XML-RPC request. That request is then sent directly to the remote server, which then processes that request and makes a new post there. Since we know that the local post is working correctly, the problem is likely happening either when creating the XML-RPC request (locally), or when handling the XML-RPC request (on the remote server), or possibly even in transport somewhere.
If I were working on this, I'd do the following:
1) Set up an account to crosspost from my 'hack to a second account on my 'hack (use 'other site' for the site, and for the URL use http://your-site-name/interface/xmlrpc). That way I could see what's happening on both sides of the post.
2) Add in some debug code in cgi-bin/DW/External/XPostProtocol/LJXMLRPC.pm to show the value that's being put in for the taglist there.
3) Add in some debug code in cgi-bin/ljprotocol.pl to show what is being received as the taglist property on crosspost.
Then go from there.
(Oh, and debug code in LJXMLRPC.pm will appear in the output of bin/worker/xpost.pl; debug code in ljprotocol.pl should appear in your Apache log.)
Hope this helps some. Good luck.