After filling out their signup form, I was disappointed to find that the submit button at the end of the form had been removed. Well, this was nothing the 'ol inspector tool couldn't solve.
To disable signups they have simply changed their type="submit" attribute to type="hidden". (see below)
After changing the attribute back to "submit" the following button appears.
Then click the button and, there you go!
The accounts aren't super useful at the moment, seeing as staking etc has been disabled due to vulnerabilities on the platform. But if you would like to secure yourself an account this method works for me.
I have notified the people at PoSW Coin through their slack channel, but am yet to hear back from them.