There does seem to be a group of people that are trying to continue and update it - some dated info talking about end of 2024 or 2025.
"On 19th of January 2022 our beloved friend Gordon died from a viciously escalating condition of leukaemia. He left memories and GRT – the tool we all have embraced in our recreational activities and profession and (as of now) has 65k+ active users around the world. It took some time to get organized and lay the ground for the continuation of his heritage. The GRT team is now more than happy to announce, we finally have managed to tackle the challenge to recreate the numeric simulation core and a basic GUI framework to recreate GRT as envisioned by Gordon. Most of the time went by in the search for the right people with the right skillset and an attitude to dedicate substantial parts of their lifetimes without compensation. We are now in the stage to assemble the major bits & pieces for a very rudimentary reimplementation of what NextGen GRT will eventually become. At the end of next Year (2024) we believe, we can provide the GRT as you know it today based on a totally-from-scratch fresh reimplementation, based on open technology and frameworks."
"But there is more to come (beginning of 2025 and onward):
- Open and crowd founded GRT pressure measurement devices
- Full isotopic simulation core
- Alternative GUIs
- GRT-Lab for loads and measurements
- Native MacOS, Android and iOS support along with Windows and a broader flavour of Linux
- Webservice based online version of GRT
- Exterior Ballistics calculators
- BC calculation wizards
- More powder models, bullets and calibres.
- DOPE recording integration
- Electronic target solutions
- Management suite for your weapons and conditions of wear and maintenance
For all of this we need to stay productive on the current level but will also have to invest in expanding the current server infrastructure (Website, GRTGitLab, GRT-Lab, WebserviceGRT…). To achieve this, we will need your support. May it be by sympathy, support for programming or simply with money. We will start our Patreon donation channel, after we have something to deliver. Be prepared for further announcements as things develop."