I have begun work on a new integration for LanguageTool in the way of implementing a server speaking the Language Server Protocol. My immediate target is Visual Studio Code; however, the server component could be used with a number of other editors.
Currently, I have both the Language Server and the VS Code extension in the same repository, though I plan split them once matured.
The Visual Studio Code extension lives at: https://github.com/adamvoss/vscode-languagetool
The language server is at: https://github.com/adamvoss/languagetool-languageserver
There is still a bit of work to go before I can publish to the VS Code Marketplace, but right now it will show the found problems for English (any variant) and replacing with the suggestions works.