It honestly probably has too many Linux developers. I'd love to develop for Linux, but the job market is super competitive, so I work building web apps (hosted on Linux). I have the skills to hack on Linux things (I build desktop Linux apps for fun), there just aren't many job opportunities.
If I could get paid something close to what I'm making now, but to work on FOSS, I'd do it in a heartbeat. But the options I see are:
fight like crazy to get one of the handful of jobs
get paid almost nothing
not work in FOSS
I don't have the energy for 1 and 2 won't work for my family, so I go for 3. I do plan to do 2 once I have enough to not need my current income (current projection is about 10 years).
OK get Linux developers then. we pay for the Software and they asked us what we want them to work on. This is one of the rare cases where Linux users can actually feel entitled to developer attention.
They need a simple GUI on top of rclone. The madlads of rclone fucking reversed engineered the drive APIs in record time. Now imagine if they were to tosh some money into that project, and then could focus only in GUI.
This backend uses the Proton-API-Bridge, which is based on go-proton-api, a fork of the official repo.
According to that page there was an official API library, provided by Proton. They forked it and added features, it didn't need to be reverse engineered.
This is an rclone backend for Proton Drive which supports the file transfer features of Proton Drive using the same client-side encryption.
Due to the fact that Proton Drive doesn't publish its API documentation, this backend is implemented with best efforts by reading the open-sourced client source code and observing the Proton Drive traffic in the browser.