Reasons game developers don’t like steam keys from sites like G2A are:

• Exploiting regional price differences.
• Splitting keys out of bundles.
• Scamming game developers for free keys (claiming they want to promote the game with a giveaway).
• Keys bought with stolen cards (that get chargebacked causing direct loss).

The last reason could apply to reselling steam accounts as well.

I think it would be very difficult to argue that that is reasonable but that would be up to the courts to decide.

Rossmann has only reuploaded the slicer fork, not any firmware (the article title is inaccurate). But yes, the slicer’s AGPL license does not apply to the firmware.

You aren’t understanding the GPL correctly.

• The GPL applies to code built on top of GPL code, this is the viral nature of the GPL.
• Anyone with a GPL license for the code can license anyone else, it does not have to come from the original creator. So Rossmann has a license granted by the creator of the fork. Also the source that Bambu Lab provide on GitHub provides a license as well.

lime

That page doesn’t say that at all. You can paywall the software and the source together for any price (but note that anyone who buys the software can now give out the source freely). Or you can charge for the source freely but only “for a price no more than your reasonable cost of physically performing this conveying of source”.