The languages are all bog standard and you can configure the environment for execution via Nix. Not on the mobile (or I've missed it) but via the website you ca

The languages are all bog standard and you can configure the environment for execution via Nix. Not on the mobile (or I've missed it) but via the website you can connect projects to git repos. So none of the data is locked in in any way. In principle, this means you should be able to clone any project and run it on your own machine(s) with little effort if you're aware of how to set up nix and git in the first place.