I'm all for it, but one thing I'm sensing is this: unlike most other kinds of software, with games the fun & gameplay are the chief and overriding factors for their audience, maybe artsy factors like visuals immersiveness etc, intangibles like replay value, all kinds of subjective factors next. Price or license politics? Way down the list, does not move the needle here for the end users, I feel.
Also of interest, hosting game assets is a whole other price category than just source code. =)
Last quarter I made a 20GB (when packaged) open-world 3rd-person game in Unreal, but the whole project folder itself was 160GB. That's basically "the source". All kinds of assets were dumped in there for experimentation & exploration & try-outs, and untangling that to strip down the project to only-what's-used-in-the-Level-file is not just not a one-click action as it should be, UE's weird reference tracking very quickly opines that everything depends on everything and nothing can be "just deleted". Would you host that whopper? I can imagine even Github wouldn't. (Haven't checked tbh — probably should have =) Because I wouldn't untangle that just to post "the source". Nobody even cares about the free downloadable ZIP (executable + content) for Linux and Windows that I made (mostly as a fun b-day gift to my bro, not per se for any other audience or any kind of adoption) and put on itch.io, who'd even care for "the source". Plus in this space it's never (at the indie level) Rocket Science, so whoever is in the coding game keeps it all home-grown self-engineered and tailored to size, and whoever isn't will forever try & fail to "plug-and-play with 3rd-party snippets".
Also of interest, many solo gamedevs or non-team creators without an artist at hand keep a vault of dear-to-their-heart pro-calibre high-quality game art assets that they may well have once received for free or very little money in the ever-coming-and-going gamedev-specific Humble Bundles, Epic / Unity / etc. store sales or freebie specials. They have thusly acquired a valid license for using them in their packaged games, but not to publish those assets' sources (if even included) with their work. Now some may stick religiously to Creative Commons / FOSS-licensed assets, but if Their Work is their chief & foremost priority rather than sporting-and-supporting "only certain types of licenses" out of some conviction — their works won't partake in your network.
This is not to rain on your parade or discourage your enthusiasm, just some things that come to mind, "to be accommodated" / considered in your pursuits. =)