This area is designed for the developers of SimSig simulations. There is no harm in non-developers looking through the public information but some information is by password access only.
First rule: please don't ask to become one. Developers have been picked by their knowledge of the subject which can be picked up from their forum postings. They can also be recommended but again proof of knowledge would be required. As we're a small band of developers, the time taken to train new developers takes up a lot of effort so it's not often new ones come on board.
This is an easier route. Again, acceptance as a tester is given by proof of knowledge and accurate bug reporting on the forum. Users are usually notified by email if we consider them to be useful. There is a brief overview of the basics of simulation construction which is intended to enable better bug reporting.