Fair point. I do agree with the "clic to execute challenge" approach.

For the terminal browser, it has more to do with it not respecting web standard than Anubis not working on it.

As for old hardware, I do agree that a temporization could be good idea, if it wasn't so easy to circumvent. In such case bots would just wait in the background and resume once the timer is fullified, which would vastly decrease Anubis effectiveness as they don't uses much power to do so. There isn't really much that can be done here.

As for the CUDA solution, that will depend on the implemented hash algorithm. Some of them (like the one used by Monero) are made to vastly more inefficient on GPU than it is on the CPU. Moreover, GPU servers are far more expensive to run than CPU ones, so the result would be the same : crawling would be more expensive.

In any case, the best solution would be by far to make it a legal requirement to respect robot.txt, but for now the legislators prefer to look the other way.