Earlier today I got tired of repairing drywall in the bathroom and downloaded Win10 for RASPI2. It is pretty easy to download and set up, but only if you are running Win10 Preview to do the SD flash.
It appear ( I could be wrong) that to develop software for this release you have to have Professional, Pro or Ultimate Visual Studio at a cost of $300 to $2,600. Maybe you can get a trial version. I my case the trial would expire before I gained any measurable proficiently.
So, while Win10 is free, it is at least $300 to develop anything useful for it.
Let me know if I am wrong about any of this. It was pretty hot in that bathroom, 97F here in SoCal.