The apps from Andreas Hegenberg are no longer available here.
Legacy versions of his apps (released before February 2018) can be used for free using this license:
However it is not recommended to use these versions as they can contain security and compatibilitiy issues and won't receive any support anymore.
A snapshot of the source code (from early 2018) for all of Andreas Hegenberg's apps can be accessed via https://boastr.net/legacy_source_code.zip (MIT license, unpack password: BTT_BST_LEGACY).
Andreas has since founded a new company (folivora.AI GmbH) which aims to develop more modern versions of these apps (and more).