[im3w1l]

Imagine if I as a hobbyist take this project A and mix it up with gpl code from another project B. I release this mashup as project C. Now some company contacts me and wants to use C commercially. If I say yes, A will be upset. If I say no, B will be upset. A contradiction!

Conclusion is that gpl but only for non-commercial does not work. They need to use a different license to get something self-consistent.

[immibis]

There's a part in the GPL that says you're free to discard any terms other than the GPL and specific ones (like attribution). So if they really did apply the GPL, you can use it commercially, but only under GPL terms.

I don't think it's that bad. Most commercial enterprises don't want their commercial products to be under GPL terms, so they'll pay for the license regardless. You should really fix the SaaS loophole by using AGPL instead though.