GREP-0027: Restructuring the GR4 repos to meet licensing needs

grep-0027-gr4-repo-structure-licensing.md

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+# GREP [0027] -- [GNU Radio 4.0 Licensing and Repo Structure]
+
+- Original Author: [Josh Morman <[email protected]>]
+- Champion: [TBD]
+- Status: Draft 
+
+History:
+- 23-Jul-2025: Initial Draft
+
+## Abstract
+
+GNU Radio 4.0 built upon the gnuradio4 repo from FAIR gives the project licensing flexibility, but also needs to 
+support the integration of GPL licensed modules.  This GREP proposes a naming and repo structure to be consistent
+with the project history, but take advantage of the permissively licensed core
+
+## Copyright / License
+
+CC-BY-ND
+
+## Motivation
+
+There is a strong desire with the introduction of GNU Radio 4.0 to have the ability to expand the userbase beyond lab based prototyping
+and allow deeper integrations into industry.  Permissive licensing of at least parts of the codebase are required
+in some scenarios to enable collaboration where previously not possible.  By making the licensing of the core (and thus derived works)
+more permissive we hope to 
+
+- Maximize adoption and enable public-private collaboration
+- Encourage contributions from a diverse ecosystem by lowering legal barriers
+- Remain free in the sense of open source principles
+- Empower submodule authors to license as desired
+- Stay compliant in evolving legal landscapes
+
+
+The repository structure should help in keeping the license distinctions clean and modular
+
+Note: No part of existing GNU Radio (3.x) is being relicensed
+
+## Description
+
+### What gets licensed as what
+
+The "core" should be MIT licensed to be compatible with the broadest range of licenses.  This includes in-tree runtime, schedulers, base classes, framework, and a minimal set of blocks.  
+
+Things that migrate from GNU Radio 3.x, or are developed by entities who desire for these blocks to be licensed as such should be GPLv3
+
+Primarily, the following GR3 modules should be migrated into GR4 as GPLv3:
+- gr-dtv
+- gr-channels
+- gr-fec
+- gr-digital
+- gr-analog (many simpler math blocks migrated elsewhere)
+- gr-zeromq
+- gr-network
+- gr-fftw (since FFTW is GPLv3)
+
+More fundamental blocks like mathematical operations, filtering, and enough processing to get to basic meaningful working examples (e.g. FM radio transmit and receive) can stay in the radio-core, or a separate MIT licensed block module
+
+### Components
+
+### Repo Structure
+
+The following should be separate repositories
+
+```
+github
+└── gnuradio
+    ├── gnuradio4
+    ├── gr4-official
+    ├── gr4-extended
+    ├── gr4-[OOT Module Name] ...
+    └── radio-core
+```
+
+#### dependencies
+
+License: Compatible with MIT
+
+Dependencies that live within the `gnuradio` workspace that radio-core will rely on need to be MIT or MIT compatible.  Currently this should only be PMT
+
+
+#### radio-core
+
+License: MIT
+
+The bulk of the current `gnuradio4` repo which includes the in-tree runtime, schedulers, base classes, framework, and a minimal set of blocks.  
+
+#### gr4-official
+
+License: GPLv3
+
+This is the set of blocks that officially developed and maintained by the GNU Radio organization and community.  
+
+
+#### gr4-extended
+
+License: ???
+
+This is the set of blocks that is perhaps more experimental or application specific in nature 
+
+
+#### gr4-[OOT Module Name]
+
+License: As inherited from the initial author
+
+Multiple OOT modules that the project inherits to maintain in the `gnuradio` workspace need to maintain the original license
+
+
+#### gnuradio4
+
+License: LGPL????
+
+This is the builder project that brings together the `radio-core` and all the supported blocksets.  Also could grab other OOTs from elsewhere on the
+internet for installation into a prefix - without becoming a custom package manager
+
+Can be built with flags such as `NOGPL` or turn on/off individual modules for building and installation
+
+
+