the hardware part was answered in the General Hardware discussion forum.
"...Would they be able to use each other's program ..."
Windows will understand windows. When you declare a network share, you will see the other computers drive as if it would be a local disk, and all interactions behave like that, although a bit slower.
Using programs stored on another computer depends on how much information is stored in the registry during installation.
It depends on the licensing scheme and the installer. Some may let you install on a networked computer, and you define the destination drive of the share as the location to install to, giving the same directory as the first installation. The code will exist once, but can be used from both machines. Of course, the machine beeing used as server must be up and running too. Please check the licensing conditions of your software.
As far as Mac is concerned, you can only run file transfers between the machines. Then you need to do file format translations on one of the two sides.
A wellknown product is MacLinkPlus from DataViz, a file format converter collection, check at <a target="_blank" href=http://www.dataviz.com/>http://www.dataviz.com/</a>. They also used to have a connection app (serial, parallel) to exchange data between the two worlds.
"...Would I have to tell my cable company ..."
as mentioned in the other post: no need.
______________
Regards - Richard