While they're not saying it's aliens, if they were saying it's aliens, the signal's strength would mean that it originated from a fairly advanced society. The commonly used scale for that discussion is the Kardashev scale, which categorizes civilizations based on technological advancement, measured by the amount of the local star's power they're able to harness. If this signal was beamed directly at Earth, it would qualify as a Kardashev Type I civilization, which isn't all that different than our own society.
If the signal was cast in all directions — an isotropic beacon — it would classify as a Kardashev Type II civilization, which would be capable of harnessing the entire power of their sun.
For now, no one is saying it's aliens. The scientists involved have found the signal noteworthy and are beginning to put telescopes in a position where more signals, if they are intentional, would be found. The SETI institute has diverted the Allen Telescope Array in northern California for continuous monitoring.