Spambots aren't against Twitters ToS. That one in particular might be part of a large bot network, but hasn't actually posted anything since 2012.
Even so, automatic posting is explicitly allowed by the developer ToS, with the only restriction that you don't cause undue load (which appears to be around how often you post).
To be clear - the only things which reliably get accounts banned on Twitter are Doxing people and actual terrorist accounts.
However (based on how Gnip and the public API work), they do some level of spam filtering by default. On some APIs you can turn that filter off.
Even so, automatic posting is explicitly allowed by the developer ToS, with the only restriction that you don't cause undue load (which appears to be around how often you post).
To be clear - the only things which reliably get accounts banned on Twitter are Doxing people and actual terrorist accounts.
However (based on how Gnip and the public API work), they do some level of spam filtering by default. On some APIs you can turn that filter off.