Looks base64 encoded to me, but running it through a decoder isn't giving me anything intelligible. Here's a OCR of the text in the image, maybe you can figure it out:
Edit: Full text is in sibling comment.
I'd guess it's gpg encrypted with the ASCII-armor enabled (which I believe is just base64 encoding).
Btw. Looks like the message is not PGP encrypted. The line lengths are different and gpg complained the message wasn't valid when trying to read the signature.