> There is less of a difference between BSL and MIT than between any GPL license, as I'm sure you are aware.
Nonsense. There is an enormous difference between the MIT license, which grants you permission to use and sublicense something without any restrictions, and the BSL, which does not.
> If I'm giving away software including source in the open, for free, while allowing redistribution and modification, then I'm not sure how to convey that without offending patrons of the OSI and FSF.
If you put limitations on how that software is used, then no, you're not giving it away. That part is something the OSI and FSF have been very clear about for decades - see e.g. the FSF's "four freedoms", which are about as clear and simple as you can get.
Even silly "camel's nose" limitations count, and have to count, otherwise there is no place to draw the line; see the OSI and FSF's comments on the HESSLA or the (pre-2021) JSLint license. Again this is something they've been clear about for decades.
> Not feeling like walking around on eggshells to give things away that's for certain.
If you want to give things away for free then do so. If you want to pull a Columbia Record Club "it's free, no wait you have to pay us" scam then of course people aren't going to support that.