Eensy is an open source project, comprised of many other open source projects, and you are welcome to contribute to it and make it better.
To build Eensy for a specific board from source, clone the projects, configure buildroot, and make.
git clone https://github.com/digitalpeer/eensy.git
git clone https://github.com/digitalpeer/buildroot.git
# where DEFCONFIG is one of the defconfig file names in eensy/configs/
make BR2_EXTERNAL=../eensy DEFCONFIG
# optionally configure more options as necessary
For more detailed instructions and further information on using and configuring your Eensy install, see the documentation.