The add-on branch for Blender 2.7 is fixed on the number 1.5. The master release for Blender 2.8 has the version number 1.6 and higher in future development.
For both add-on versions the same library is used, so all BIS materials are available for all add-on versions, however, please note, materials made for Blender 2.8 may not look correct in Blender 2.7 and backward.
Now the download consists of two archives to install the add-on:
The BIS library is free and fully accessible for all users. Any content (materials or meshes) from the open part of the library can be downloaded by any user without any restrictions. So why do you need a pro- account?
At first, this is a way to support the project. Like any other free project, BIS needs for users support. However, the BIS pro- account is not only a status attachment. The pro- status does not provide any additional content, but it allows you to make your pipeline with BIS more convenient.
Blender has its own built-in text editor for writing scripts and add-ons, but it’s much convenient to develop them in external IDEs that provide the user with more features such as autocomplete, syntax highlighting, integration with version control systems and other tools that make development faster and easier.
One of these IDEs is Visual Studio Code from Microsoft. This is a free universal environment that supports development with various programming languages, including the Blender API language – Python.