Even if Snap closes you in to use the Snapchat app with the glasses, you don't have to upload the snaps anywhere. You can just save it to your phone like an ordinary camera app.
Viewing the videos on Snapchat you rotate your phone depending on whether you want a horizontal or vertical frame, which is actually pretty cool. When saved outside of Snap the videos save to some standard video format as a circle within a rectangular frame, which makes them kinda useless.
I saw your comment and the parent comment and didn't think I would see that video posted. That was the first video I thought of to answer the question. In case the parent poster is wondering, here is what the exported video looks like:
1. Take video
2. Enable BT and WiFi on your smartphone
3. Open Snapchat on your smartphone
4. Wait for what seems like forever for the phone to find the Spectacles. Charging them in the case seems to help, as does charging the phone?
5. Wait for the phone to grab the low res version.
6. Wait for the phone to grab the "HD" version. (Note: this may (?) be automatic on iOS. I own an LG V20.)
7. Navigate through Snapchat's terrible interface to the video you want to save.
8. Save to your phone. You're done!
They come out as 800x800 videos that are circular, so the true resolution is (-21.4% vs square).