The issue with the GPL isn't about being able to download source code. It's unambiguous that they are complying with that requirement. The issue is the sentence

The issue with the GPL isn't about being able to download source code. It's unambiguous that they are complying with that requirement. The issue is the sentence "You may not impose any further restrictions on the recipients' exercise of the rights granted herein." They're violating that by disallowing the people they do give the source code to from publicly mirroring it (on pain of terminating their contract).