The title of this post took me about 3 attempts to parse, because "OS" is more strongly bound to Operating System in this context (but presumably it's supposed to read as Open Source)
Yes, super sorry about this. I meant to write OSS but forgot an S, and now it's too late to edit the post. But yes this could FOSS since it's a free tool with MIT license.
Yes, I think OP wanted to say OSS (last S = Software).
Edit: Did a quick google search and it seems like the acronym OSS has fallen out of prominence. Probably best to explicitly state “Open Source” nowadays to avoid any confusion.