They will only be able to download apps that were grabbed directly from the Google Play Store (or other official app stores), according to TechCrunch. This is a logical move on the surface — third-party apps can pose a risk to those who don’t know what they’re doing, and APP users are generally going to care more about security and privacy than others.
However, APP participants are also likely to be pretty tech-savvy, and it’s not that difficult to avoid downloading malware-ridden third-party apps if you know what to look for.