I have a Paypal label from an Ebay transaction that for whatever reason never made it into the mail.  I fully refunded my Ebay buyer but it was too late for me to void the label on Paypal (they only allow you to do that within 48 hours of postage purchase).  I've already purchased this postage, but it was never scanned/sent.  The value of the postage is about what a lightweight book would cost to send.   Is it possible for me to use the postage part of this label but ship it to a different address?  I expect I'd need to cut off the delivery confirmation part, as it is to a different address, but is this at all feasible/allowable under USPS?

From the USPS FAQs:

Can I cut-off the PC Postage (indicia) part of the label and use it separate from the online label?

No, online labels can only be used as a whole, the way they were printed. Do not photo copy or alter the label.

Nope, it is only good for the address you entered in. There might be a little wiggle room with dates and weights (adding additional postage to it) but the address itself is set in stone.

Just Cancel the label.  I think you have a time frame to do this.  USPS/Paypal has a record of wehterh the label has been used or not used.

In 10 days, you will receive a refund from USPS thru Paypal.

I've had to cancel labels before and always got my $ back.