If you grab an old version...
https://github.com/bistromath/gr-ais/tr ... 9f91e869a2
The bootstrap file is there. It would appear that they have changed their build process, and not updated their documentation, as you had thought.
The commit that overhauled the build states "cmake is the future", however, I wouldn't call autoconfig/make an obsolete system (just about every current project uses it).
I would suggest you will need to do some Google on the 'cmake' product, it would appear likely that you'll need to install cmake itself as a first step.