I used this binding up to OH 3.4.5 so it is compatible.
Error looks more the way that there’s a conflict of 2 parallel installed PV Forecast bindings. Saw this also for other bindings.
My suggestion is to clean up your current installation from any Forecast Solar installations: Follow instructions below. It’s the same problem as for MercedesMe binding but I think you can easily adapt to Solar Forecast.
I’m pretty sure after this cleanup and a fresh restart the 3.4 binding will work after dropping it into the addons folder.