TL/DR: we only store data if we can't avoid that; we don't share anything.
We respect your privacy and under no circumstances will share any of your personal information to any third party or use it in any way other than to provide you this service.
We store account data necessary for the service to function: Slack user id, Skype user id, first name, last name and your e-mail associated with PayPal.
The latter is only used for payment identification; we will not send any e-mails to it.
We do not cache, log or otherwise store your messages. After our software forwards them to Slack/Skype, they are gone from our servers forever.
All communications (Skylack-Slack, Skylack-Skype, Skylack-Paypal) are SSL-encrypted.
We automatically remove your account and all data associated with it 1 month after your subscription becomes inactive. Please contact us in case you require immediate removal.
Please don't hesitate to contact us with any concerns regarding your privacy with our service.