Deere has made the components available for any third-party software company to write prescriptions for the GreenStar hardware, at no charge to the grower, service provider, or third-party software company.   Actually, writing prescriptions for the GS2 is pretty easy (GS1 is not).  It's reading the as-applied data that is quite difficult.  

Were I in your place, I would never let my service provider's ability to write prescriptions in a specific format influence my hardware decision.  You will live with your hardware decision for years.  Your vendor's software package may be able to write prescriptions for Deere hardware within a few months.   If not, you have options for getting those prescriptions converted to any format you want.  You can do any required conversions yourself, or just make your service provider do it for you as a requirement for your business.

It sounds like you are looking for a reason to switch vendors, and it is not my intent to dissuade you from that.  I just wanted to clarify the ability to write Deere prescriptions for others that might read this thread.