I am also keeping a list of previous versions so that you can rollback when a new version is not working for you.
To manually install GPS Essentials, you need to install APK-Files. You don't need a rooted device, but you will have to enable "Unknown sources" in your device's security settings.
You can simply click on one of the links at the bottom of this page to install GPS Essentials. If it doesn't work, you might have to install and installer first.
Every version has a minor number which is the second number in the version string.
The versions with an even or zero minor number, e.g. 2.0 or 2.2 are final versions. These are stable releases that have gone through thorough testing. The versions with odd minor numbers, e.g. 2.1 or 2.3 are beta releases. These releases contain new features, but they might also be less stable.
As opposed to the above numbering scheme, version 4.0 is in beta testing, yet.
You can also install beta versions from Google Play. To do so, join the GPS Essentials Beta Testing Group on Google+, then click on "Become a tester" in that group. You can receive automatic updates through Google Play then, but switching between the beta and production versions requires a bit more work.
Please send me an email if you notice something is wrong.