Startups and midsized companies do the same all the time. Are you drawing the line on profit? Number of employees? As others have said, if you want to make a p

Startups and midsized companies do the same all the time. Are you drawing the line on profit? Number of employees? As others have said, if you want to make a political statement go for it and name all the companies you don't want using your software explicitly (and keep updating that when they work around you). Personally, I wouldn't bother. If this is for a business idea, rethink your revenue strategy... licensing alone is a nightmare to enforce.