In some countries Google Play offers ebooks. I was wondering if those are DRM protected.
Can I export them as e.g. epub? Or are they bound to be read within the Google
Play Books application?
Some are DRM protected, others aren't.
One way I'm aware of to find out the ones that are DRM, is when you try to download the file for offline reading:
.acsm then its a DRM protected book.
.pdf then its not DRM.
Related to exporting the eBook to a certain format or have it restricted to be read on Google Play, the above first link answers your doubt, where they stat that you can read or download to read your eBook on other devices or applications.