Hello Arthur,
I’m not an expert on .htacess files, but by the look of things, it is to do with disabling the GZIP Compression (If you have it active) when dealing with s2Member File Downloads.
Now, I can’t say for certain the impact this’ll have, but I assume it will cause some issues when downloading files from s2Member itself. If all your downloads are handled by other plugin, you shouldn’t experience any issues.
Personally, I would test this to be certain. Set up a new environment (or a page / area members can’t access) and assign a download from both your Easy Digital Download Plugin, and also from s2Member. If you’re not hitting any issues with allowing s2Member Downloads without the code, I would assume it isn’t critical.
However, what I will mention is that s2Member does allow for people to buy certain downloadable content through Buy Now buttons, so the addition of another plugin into your site, to handle a service already provided might be problematic.
I know we’ve switched several of our services over to s2Member, simply because of how reliable they are with their updates, improvements and fixing any issues that WordPress updates may cause.
Carefully assess the implications of additional software when you’ve got a system already capable of performing the same task, especially when it comes to paid services.