I need to build a scripting interface for my C# program that does system level testing of embedded firmware.
My application contains libraries to fully interact with
From the DSL you're going for, I'd recommend to use CUCUMBER with IronRuby.
With Cucumber, testers write tests that look something like that:
Scenario: See all vendors
Given I am logged in as a user in the administrator role
And There are 3 vendors
When I go to the manage vendors page
Then I should see the first 3 vendor names
It is very easy to make this language fit your needs. Just google "Cucumber and IronRuby" and you'll find several guides and blog posts to get you started.