The QB64 community is aware of FreeBASIC, but a big feature of QB64 is that you can literally drop QBasic code into QB64 and it will work without any modifications. This won't work at all for FreeBASIC, it's much to far away from QBasic. FreeBASIC is still a nice language, but it does have different goals then QB64.

They've moved away then, since I last used it, earlier versions were pretty compatible. QB64's aims are good, but it's still incomplete itself, and I had stability issues with it (and to be honest, wasn't particularly keen on still using the old QB IDE anymore either).

FreeBASIC definitely has moved away from QBasic compatibility, I don't think it's considered a focus at this point. The last SDL versions of QB64 are fairly impressively compatible IMO, a large chunk of QBasic programs work without too many modifications. You can also now use the compiler via the command-line if you're interested. Back when I was doing some more "serious" QB64 development, I use a regular IDE and shell'd out to QB64 to compile, rather then typing in the QB64 IDE itself. It has it's share of rough edges though, so it is what it is.