The register
The register lists Railsimulator.com t/a Dovetail Games in Chatham, Kent as a licensed sponsor on Skilled Worker, an entry that goes back to at least 2026. Its rating on the register is Worker (A rating).
Companies House lists it as Railsimulator.com Limited, number 06751125, incorporated 2008: 17 years of filings behind the name. Registered office: 3rd Floor North, Fitted Rigging House, Anchor Wharf, The Historic Dockyard, Chatham, Kent, ME4 4TZ, ME4 4TZ. By its SIC codes the business is in it, software and media.
Holding a licence is the expensive, slow part done. For Railsimulator.com t/a Dovetail Games the question each time is only whether the role and the pay fit the current rules, and that is checked per vacancy.