InfoPath Dev

My company would like to use InfoPath and SharePoint Server 2007 to let our folks request time off - without liscensing InfoPath Form Services for our server. 

I've a form in shared documents: open the form, complete, submit, and it emails to the right place. Very simple and it works great with one catch - about 10% of our folks are software engineers running Linux.  They use open source software for any MS Office needs.

Can you recommend an open source software that will allow our Linux them to complete and submit the form?  Or do you have any other suggestions?

You could check with Adobe. The real trick is going to be getting the open source to work with your SQL database (this is possible though).