14 DAY TRIAL // Flatpak developer and maintainer Alexander Larsson released earlier today Flatpak 0.9.10, the latest version for the 0.9.x series of the Linux application sandboxing and distribution framework (formerly XDG-App).
While Flatpak 0.9.10 is a hotfix release that addresses a regression from version 0.9.9 in the D-Bus proxy, which made various apps to no longer function properly, Flatpak 0.9.9 (full changelog attached below) was published this past weekend with more enhancements, including the split of the flatpak-builder command into a separate tool that application developers can use to package their apps as Flatpaks.
Therefore, Flatpak-builder is now an open-source, standalone utility that can be downloaded from its own GitHub page, and it's designed as a wrapper around the flatpak build command to be used for building Flatpaks from sources. This is a smart move from the Flatpak team as it should boost the adoption of the Flatpak format across more GNU/Linux distributions.
Here's how to install Flatpak-builder on your Linux OS
Building a Flatpak from sources, or in other words packaging a Linux app that's only available as a source tarball into the Flatpak format, it's quite easy with Flatpak-builder. All you have to do is to download and install Flatpak-builder using the following commands, using the traditional autoconf-style build mechanism.
./configure [args]
make
sudo make install
Please note that Flatpak-builder relies on Flatpak, so you should make sure it's also installed before installing the tool using the above commands. Once Flatpak-builder is installed, you will be able to use it via the command-line to package your apps as Flatpaks. Detailed instructions are available here, where you'll also find all the information you need to get started with building Linux apps as Flatpaks for easy distribution across multiple OSes.