I mean it still seems to work but yes concerns would be vulnerabilities, future compatibility the usual. Usually when the original owner decides to abandon it they do give the option for others to take up the maintenance. I am not a developer just a user of the plugin. I am not sure how long it goes before WordPress removes them for lack of updates either.
It is not necessary to create a fork of the plugin. The code of the plugin is public – https://github.com/bueltge/adminimize, and each helping hands are really gladly seen, for the development part and also for the support area. See the sticky threads at the support forum.
But, there are a no contribution since longer time, no supporting hands on the support forum or the code maintenance.
@bueltge thanks for chiming in. I for one appreciate what the plugin does to help me. I hope that some people can step up to help support and maintain it. It’s a very powerful plugin and AFAIK the only one of it’s kind.