Not at all. This is a fundamental feature of Android as an open source system. You just need to download the file and install. It will ask you to agree to install unverified apps, then you are good. You shouldn't need to use developer mode either. Many big organisations do this to avoid Google's cut of 30% on all transactions. Epic do this for Fortnight because a Google managed 30% cut on every micro transaction would be a right pain. The Google Play store is just a walled garden for payment processing, marketing, indexing, quality control and censorship.