No, they are separate software, with separate licenses.
The C2 runtime is available in C3 as a backwards compatibility option, since C2 projects can be opened in C3, in case there were cases where some old projects did not behave as expected with the C3 runtime.
Generally speaking the C3 runtime works fine for C2 projects as well AFAIK, so the C2 runtime option will probably be rarely used in the future.
If you want to use C2, I believe you can still purchase it as a one time purchase for lifetime access.