Licenses for popular open source components:
- libgcc_s and libstdc++: GPL but with GCC Runtime Library Exception which enables one to use it in proprietary software: please see here and and here
- glibc (libc, libm, librt, libdl, libpthread, ld-linux-x86-64): LGPL 2.1
- zlib: custom permissive license
- openssl: Apache License 2.0
- tcmalloc: Apache License 2.0