On my debian-system, I just added a wxClient-class to C::B (with #ifndef __wxMSW__) and reused the most part of the actual DDEServer for MSW to open a file inside a running C::B-process.
For test-purposes I hardcoded the filename, and it worked as expected.
If it will be implemented the question is, how should it work ?
Shall it always try to open a given file in a running instance of C::B, or only if multiple instances are not allowed, or should another instance of C::B only be opened if no filename is given on commandline, or ...
I hope I found some more time this week and maybe this weekend to work on it a little more.