It sounds flippant, but it's the truth. They'll use it internally. They'll expose it to the outside but delete all of the license information. They'll use it but stick a crappy React front-end in front of the rest (whether or not that counts as "using AGPL licensed software in violation of the license" is a matter for lawyers to figure out). Or they'll just use it because they have way more money than the AGPL-licensed project and drag it out in court for however long it takes.
This is a good, short read. For those who are unfamiliar with the AGPL license that the author proposes we all start using, the main difference (and I am not a lawyer) is that under the AGPL, the source code including any modifications must also be made available to all users interacting with the software over a network. This prevents companies from making proprietary versions of AGPL software that are only accessible as a web service, which is one of the big ways that corporations are able to profit from GPL source code contributions these days.
I think Codeberg is totally open as opposed to GitLab which has an open core and paid enterprise version. There's also SourceHut but you have to pay to use it (no free tier). As far as I know there aren't any public Forgejo instances.(Codeberg is Forgejo)
I think any of these are better than GitHub (I say as I still use GitHub).