Is it illegal to market and sell an application written using Excel?

Question

If it is, I wonder if they'd allow it as long as they get a cut.

Answer 1

Nope there are plenty of companies that do it.  Here is one.

http://www.biznetsoftware.com/

I write my own VBA applications for Access and Excel all the time.

Answer 2

It's totally fine to market and sell an application written using Excel.  You are the one that wrote the application.  It's not like you are selling Excel itself.