I’d be a little nervous about adding any Sonos account data to a third party app, that’s not the way the Sonos ecosystem works. Normally speaking, the streaming company adds themselves to the Sonos ecosystem by following the instructions at the Sonos partners page, after which their stream would appear in the Sonos controller as an option to ‘add’. It doesn’t, to my knowledge, work in any other way, including adding your account data to their own app/account system. 
 

You may want to contact them directly and ask them exactly what the process is, and why they want to to share your Sonos account data with them (which you used to log in to both your Sonos system and this forum). 

Yeah, that is a suspicious login dialog, it is NOT the Sonos login so I would not put my Sonos credentials into it.

Thank you both for your replies. It is strange because iChill is in Sonos ‘Add a service’ option. I would’ve easily think it’s credible. Below are photos in sequence until it reaches the login page of iChill  thank you for your advises! 

The Sonos integration for this service looks a bit incomplete, and not just at the login phase, this is an unfinished piece I saw when I tried to add the service:

I *think* the login dialog the user posted is actually mis-worded, and it is asking you to login to your iChill account as a part of the Sonos linking process, but I haven’t tried that.