The weather script is a separate program from the firmware, so there is no need to install the weather program on the same controller — if you have a Raspberry Pi or just any Linux box, you can still the weather program on that computer and point the weather url on your OS to that computer. The WU support is already available on the official OpenSprinkler weather server as I described here:
https://opensprinkler.com/forums/topic/announcing-the-new-et-algorithm-and-weather-service-changes/
however, you won’t see it in the user interface until we release firmware 2.1.9.