I heard about Grammarly to check the grammar of your writings. It’s not opensource, so what are the alternatives?

Editsaurus

For english, a good little tool is editsaurus. The website is now offline, however it may be doable to download the code and serve locally. The sources used by the author are worth reading as well, regarding adverbs and useless words.

Grammark

An simple, efficient and free online tool, for english and academic writing:

grammark.org

LanguageTool

Works for several languages, but some features require paying for a premium account.

languagetool.org

Grammalecte (french)

This is for French only: grammalecte.net. It is installable as modules for separate programs, such as Libreoffice, Thunderbird or Chrome.

Needed: Libreoffice or Vim plugins

The above online tools are helpful, but plugins for Libreoffice and my text editor of choice would be smoother. Do you know any?