They only want money for providing the build. The source code and build scripts are free/libre. From the website: How do I install Conversations? Convers

They only want money for providing the build. The source code and build scripts are free/libre. From the website: How do I install Conversations? Conversations is entirely open source and licensed under GPLv3. So if you are a software developer, you can check out the sources from GitHub and use gradle to build your APK file. The more convenient way — which not only gives you automatic updates but also supports the further development of Conversations — is to buy the App in the Google Play Store. Buying the App from the Play Store will also give you access to our beta test.