There is an open source MetaTrader trade copier at [url removed, login to view] There are recent changes in the Google SVN repository regarding the following:
1. Partial closes
2. Filtering out based on the account number on the Master account
Unfortunately, these changes have not yet been tested and adjusted accordingly. This project is to test out and revise the changes as necessary to make these features work.
The C++ dll is a CodeBlocks project ([url removed, login to view]) and should compile cleanly in the latest CodeBlocks + MinGW release.