> Just because I can hex edit Photoshop.exe to say what I want in the about dialog doesn't make it open source, even if it is faster and easier to hexedit it than it is to recompile from source.

First, licenses matter. Photoshop.exe is closed source first and foremost because the license says so.

Second and more importantly for this discussion, Adobe doesn't prefer to work with hexedit, they prefer to work with the source code.

OpenAI prefers to fine tune their existing models rather than train new ones. They fine tune regularly, and have only trained from scratch four times total, with each of those being a completely new model, not a modification.

That means the weights of an LLM are the preferred form for modification, which meets the GPL's definition of 'source code':

> The “source code” for a work means the preferred form of the work for making modifications to it.