I thought proprietary project could use GPL code, even for commercial offerings, without releasing the code. If they packaged it and sold it to you as something you ran, then it's a GPL violation. That's the whole reason AGPL was created, because people were doing "cloud offerings" of GPL stuff with their mods without releasing those modifications.
That's also how you get non-FOSS licenses like the Redis license, the Elastic license, etc. .. You know, I highly doubt the AGPL would be approved as an OSI compliant open source license if it was written today.