Just been looking at the threading building blocks, and as their license, they say it's the GPLv2 with the runtime exception. On the Intel page itself they say that the commercial license is the right one if you need commercial support.
So what's the deal if I'm doing a commercial, closed source application which uses the TBB, but I don't need commercial support? Can I still use the open source version, or is this a case where I have to buy the commercial one?
After all, I assumed that I can use the libstdc++ in a commercial application without restrictions (i.e. link against it).
I believe your understanding is correct. If you need commercial support from Intel, then you should pay for a commercial license. If you simply want to use the library, even in a closed source application, you should be fine.
The LibSTDC++ FAQ covers this issue concisely.
来源：https://stackoverflow.com/questions/362694/intel-s-threading-building-blocks-runtime-exception-license-what-does-it-mean