Is it uncommon to do some free software work in your spare time? I usually have a bunch of things I want to fix and spend an hour or two during the weekend when I would normally be just watching YouTube.
If it's "work work" (tasks you're being employed to do) then it's illegal in most of the EU to work every day — see the Working Time Directive¹, which requires at least 24 hours of non-work time every week, for most occupations.
I'm paid to work on free software. In the last year, my Github profile shows a single commit on a weekend, when I made a pull request on a browser extension I use. I'd rather spend my weekend time away from computers :)
> an adult worker is entitled to an uninterrupted rest period of not less than 24 hours in each seven-day period
The key word is "entitled", meaning that an employer cannot force them to work (or fire them if they don't work). The worker can choose to do whatever they want with their time, so long as they retain the right to exercise their legally permitted break.
It would be a very weird law to not allow a worker to do any work related to their job during their free time. Would that mean that a musician couldn't play music during their free time?