yeah then it gets trickier...
let's start by saying something, i've used weather watcher for a couple years now, and i have the new version installed now. no sign of anything bad from it.
but i do see a WhenU/SaveNow version of Weather Watcher on the website, and as you say this is not simply displaying adware in the application, but rather it does stuff to your internet explorer or otherwise lives on your system and pops up ads.
although this is not spyware i view such extreme adware as unacceptable, and i would never install such a program that included it on my computer.
however i cant help but be sympathetic to an author who it seems to me is just trying to get a little money back from software that he has always made available (and continues to make available without ads) free.
where i would fault the author of weather watcher is not more clearly on the website explaining the consequeunces of installing the adware version.
all things considered, i would not hold back a recommendation of weather watcher because of this, but i would make VERY clear to people that they should NOT install the adware version.
if it was just ads inside the app i would have different advice, i'd say install the ad version if you dont mind ads and want to support developer. in this case if you want to support developer, he has a donation button - send him a donation and include a note encouraging him to stop using such adware.
he's probably going to get plenty of hate mail from people who accidentally install the adware version and are quite upset so go easy on him
