First, this is absolutely NOT my code; I lifted the relevant lines from an old version of the commercial dbDOS fork. It adds (Win32 only) clipboard pasting into DOSBox. I assigned the keystroke Ctrl-Alt-F4 for pasting, but that's easily changed.

I prepared a DIFF based on current SVN and have attached it and an executable (apologies for the icon; it's the one I use in my own DOSBox-based project).

I hope this might be useful to someone. It may or not be relevant to games, and if it's completely irrelevant to games, I apologize for wasting bandwidth on it.

It's the same code (slightly rearranged) that recently got merged into DOSBox-X. Again, this is NOT my code, and I don't pretend to understand it. But it seems to work.