Google plans to introduce restrictions on installing applications by developers who have not proven their identity to Google, which is neither
- "Locking" in the sense that you can't turn it off. The process they describe is obnoxious, an unreasonable imposition on your ability to use your device as you see fit, and likely to result in some open source developers abandoning the platform, but "locking" is too strong. The link answers what I think you're asking, which is how to allow installing whatever apps you see fit.
- A requirement to use Google's store. Many FOSS apps for Android are from developers registered with Google. If it's in the Play Store as well as F-Droid or the developer's website, they're already registered.