What I infer from these (admittedly few) facts is that you probably have to use the same compiler as ActiveState if you want to move modules/libraries like the OP wants, so getting a freeware compiler won't probably help.
I believe whatever compiler ActiveState uses, it would be compatible with the Free-to-use command-line version of MSC that Microsoft distributes.
I would caution that I've never tried this, however, so there might well be some aspect of using this compiler to integrate XS modules into ActiveState that I'm not considering. If this didn't work directly, I suspect that one could download the ActiveState code and rebuild it with this free compiler and then do XS/dll development with the resulting system.
